diff --git a/compiler/Main.hs b/compiler/Main.hs
index dfbed52d10..5e0565e6ec 100644
--- a/compiler/Main.hs
+++ b/compiler/Main.hs
@@ -112,11 +112,11 @@ csCodegen options@Cs {..} = do
     typeMapping = if collection_interfaces
             then csCollectionInterfacesTypeMapping
             else csTypeMapping
-    fieldMapping = if readonly_properties
-            then ReadOnlyProperties
-            else if fields
-                 then PublicFields
-                 else Properties
+    fieldMapping
+      | readonly_properties = ReadOnlyProperties
+      | init_only_properties = InitOnlyProperties
+      | fields = PublicFields
+      | otherwise = Properties
     constructorOptions = if constructor_parameters
             then ConstructorParameters
             else DefaultWithProtectedBase
diff --git a/compiler/Options.hs b/compiler/Options.hs
index 573c8d5c6d..236fe11412 100644
--- a/compiler/Options.hs
+++ b/compiler/Options.hs
@@ -53,6 +53,7 @@ data Options
         , namespace :: [String]
         , collection_interfaces :: Bool
         , readonly_properties :: Bool
+        , init_only_properties :: Bool
         , fields :: Bool
         , jobs :: Maybe Int
         , no_banner :: Bool
@@ -106,9 +107,10 @@ cs :: Options
 cs = Cs
     { collection_interfaces = def &= name "c" &= help "Use interfaces rather than concrete collection types"
     , readonly_properties = def &= name "r" &= help "Generate private property setters"
+    , init_only_properties = def &= name "init-only" &= help "Generate init-only property setters"
     , fields = def &= name "f" &= help "Generate public fields rather than properties"
     , structs_enabled = True &= explicit &= name "structs" &= help "Generate C# types for Bond structs and enums (true by default, use \"--structs=false\" to disable)"
-    , constructor_parameters = def &= explicit &= name "preview-constructor-parameters" &= help "PREVIEW FEATURE: Generate a constructor that takes all the fields as parameters. Typically used with readonly-properties."
+    , constructor_parameters = def &= explicit &= name "preview-constructor-parameters" &= help "PREVIEW FEATURE: Generate a constructor that takes all the fields as parameters. Typically used with readonly-properties or init-only-properties."
     } &=
     name "c#" &=
     help "Generate C# code"
diff --git a/compiler/src/Language/Bond/Codegen/Cs/Types_cs.hs b/compiler/src/Language/Bond/Codegen/Cs/Types_cs.hs
index 50854607bf..a136d03d27 100644
--- a/compiler/src/Language/Bond/Codegen/Cs/Types_cs.hs
+++ b/compiler/src/Language/Bond/Codegen/Cs/Types_cs.hs
@@ -31,7 +31,8 @@ data StructMapping =
 data FieldMapping =
     PublicFields |          -- ^ public fields
     Properties |            -- ^ auto-properties
-    ReadOnlyProperties      -- ^ auto-properties with private setter
+    ReadOnlyProperties |    -- ^ auto-properties with private setter
+    InitOnlyProperties      -- ^ auto-properties with init-only setter
     deriving Eq
 
 -- | Options for how constructors should be generated.
@@ -186,6 +187,7 @@ namespace #{csNamespace}
                 PublicFields        -> [lt|#{optional fieldInitializer $ csDefault f};|]
                 Properties          -> [lt| { get; set; }|]
                 ReadOnlyProperties  -> [lt| { get; private set; }|]
+                InitOnlyProperties  -> [lt| { get; init; }|]
             fieldInitializer x = [lt| = #{x}|]
             new = if isBaseField fieldName structBase then "new " else "" :: String
 
diff --git a/compiler/tests/TestMain.hs b/compiler/tests/TestMain.hs
index ca60f46b8b..aa1b745863 100644
--- a/compiler/tests/TestMain.hs
+++ b/compiler/tests/TestMain.hs
@@ -151,6 +151,13 @@ tests = testGroup "Compiler tests"
                 ]
                 "complex_inheritance"
                 "constructor-parameters"
+            , verifyCodegenVariation
+                [ "c#"
+                , "--preview-constructor-parameters"
+                , "--init-only-properties"
+                ]
+                "complex_inheritance"
+                "constructor-parameters_init"
             , verifyCodegenVariation
                 [ "c#"
                 , "--preview-constructor-parameters"
@@ -180,6 +187,13 @@ tests = testGroup "Compiler tests"
                 ]
                 "empty_struct"
                 "constructor-parameters"
+            , verifyCodegenVariation
+                [ "c#"
+                , "--preview-constructor-parameters"
+                , "--init-only-properties"
+                ]
+                "empty_struct"
+                "constructor-parameters_init"
             ]
         , testGroup "Java"
             [ verifyJavaCodegen "attributes"
diff --git a/compiler/tests/Tests/Codegen.hs b/compiler/tests/Tests/Codegen.hs
index e997b1d7db..b174b8cf5f 100644
--- a/compiler/tests/Tests/Codegen.hs
+++ b/compiler/tests/Tests/Codegen.hs
@@ -91,11 +91,11 @@ verifyFiles options baseName variation =
     extra options
   where
     verify = verifyFile options baseName
-    fieldMapping Cs {..} = if readonly_properties
-        then ReadOnlyProperties
-        else if fields
-             then PublicFields
-             else Properties
+    fieldMapping Cs {..}
+      | readonly_properties = ReadOnlyProperties
+      | init_only_properties = InitOnlyProperties
+      | fields = PublicFields
+      | otherwise = Properties
     constructorOptions Cs {..} = if constructor_parameters
         then ConstructorParameters
         else DefaultWithProtectedBase
diff --git a/compiler/tests/generated/constructor-parameters_init/collection-interfaces/complex_inheritance_types.cs b/compiler/tests/generated/constructor-parameters_init/collection-interfaces/complex_inheritance_types.cs
new file mode 100644
index 0000000000..07b45e2a00
--- /dev/null
+++ b/compiler/tests/generated/constructor-parameters_init/collection-interfaces/complex_inheritance_types.cs
@@ -0,0 +1,210 @@
+
+
+// suppress "Missing XML comment for publicly visible type or member"
+#pragma warning disable 1591
+
+
+#region ReSharper warnings
+// ReSharper disable PartialTypeWithSinglePart
+// ReSharper disable RedundantNameQualifier
+// ReSharper disable InconsistentNaming
+// ReSharper disable CheckNamespace
+// ReSharper disable UnusedParameter.Local
+// ReSharper disable RedundantUsingDirective
+#endregion
+
+namespace Test
+{
+    using System.Collections.Generic;
+
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public enum TestEnum
+    {
+        EnumVal1,
+        EnumVal2,
+        EnumVal3,
+    }
+
+    [global::Bond.Schema]
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public partial class Simple
+    {
+        [global::Bond.Id(0)]
+        public int someInt { get; init; }
+
+        [global::Bond.Id(1)]
+        public int anotherInt { get; init; }
+
+        [global::Bond.Id(2), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        public string someString { get; init; }
+
+        public Simple(
+            int someInt,
+            int anotherInt,
+            string someString)
+        {
+            this.someInt = someInt;
+            this.anotherInt = anotherInt;
+            this.someString = someString;
+        }
+
+        public Simple()
+        {
+            someString = "";
+        }
+    }
+
+    [global::Bond.Schema]
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public partial class Foo
+    {
+        [global::Bond.Id(0), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        public string someText { get; init; }
+
+        public Foo(
+            string someText)
+        {
+            this.someText = someText;
+        }
+
+        public Foo()
+        {
+            someText = "BaseText1";
+        }
+    }
+
+    [global::Bond.Schema]
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public partial class Bar
+        : Foo
+    {
+        [global::Bond.Id(0)]
+        public TestEnum testEnum { get; init; }
+
+        [global::Bond.Id(1), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        new public string someText { get; init; }
+
+        [global::Bond.Id(2)]
+        public int someInt { get; init; }
+
+        [global::Bond.Id(3), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        public string moreText { get; init; }
+
+        [global::Bond.Id(4), global::Bond.Type(typeof(List<Simple>))]
+        public IList<Simple> someList { get; init; }
+
+        [global::Bond.Id(5), global::Bond.Type(typeof(Dictionary<global::Bond.Tag.wstring, double>))]
+        public IDictionary<string, double> someMap { get; init; }
+
+        [global::Bond.Id(6), global::Bond.Type(typeof(HashSet<global::Bond.Tag.wstring>))]
+        public ISet<string> someSet { get; init; }
+
+        public Bar(
+            // Base class parameters
+            string someText,
+
+            // This class parameters
+            TestEnum testEnum,
+            string someText0,
+            int someInt,
+            string moreText,
+            IList<Simple> someList,
+            IDictionary<string, double> someMap,
+            ISet<string> someSet
+        ) : base(
+                someText)
+        {
+            this.testEnum = testEnum;
+            this.someText = someText0;
+            this.someInt = someInt;
+            this.moreText = moreText;
+            this.someList = someList;
+            this.someMap = someMap;
+            this.someSet = someSet;
+        }
+
+        public Bar()
+        {
+            testEnum = TestEnum.Val2;
+            someText = "DerivedText1";
+            moreText = "";
+            someList = new List<Simple>();
+            someMap = new Dictionary<string, double>();
+            someSet = new HashSet<string>();
+        }
+    }
+
+    [global::Bond.Schema]
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public partial class Baz
+        : Bar
+    {
+        [global::Bond.Id(0), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        new public string someText { get; init; }
+
+        [global::Bond.Id(1), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        public string evenMoreText { get; init; }
+
+        [global::Bond.Id(2), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        public string someText1 { get; init; }
+
+        public Baz(
+            // Base class parameters
+            string someText,
+            TestEnum testEnum,
+            string someText0,
+            int someInt,
+            string moreText,
+            IList<Simple> someList,
+            IDictionary<string, double> someMap,
+            ISet<string> someSet,
+
+            // This class parameters
+            string someText1,
+            string evenMoreText,
+            string someText10
+        ) : base(
+                someText,
+                testEnum,
+                someText0,
+                someInt,
+                moreText,
+                someList,
+                someMap,
+                someSet)
+        {
+            this.someText = someText1;
+            this.evenMoreText = evenMoreText;
+            this.someText1 = someText10;
+        }
+
+        public Baz()
+        {
+            someText = "";
+            evenMoreText = "";
+            someText1 = "";
+        }
+    }
+
+    [global::Bond.Schema]
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public partial class DerivedEmpty
+        : Foo
+    {
+        
+
+        public DerivedEmpty(
+            // Base class parameters
+            string someText
+        ) : base(
+                someText)
+        {
+            
+        }
+
+        public DerivedEmpty()
+        {
+            
+        }
+    }
+} // Test
diff --git a/compiler/tests/generated/constructor-parameters_init/collection-interfaces/empty_struct_types.cs b/compiler/tests/generated/constructor-parameters_init/collection-interfaces/empty_struct_types.cs
new file mode 100644
index 0000000000..eddf7b0689
--- /dev/null
+++ b/compiler/tests/generated/constructor-parameters_init/collection-interfaces/empty_struct_types.cs
@@ -0,0 +1,30 @@
+
+
+// suppress "Missing XML comment for publicly visible type or member"
+#pragma warning disable 1591
+
+
+#region ReSharper warnings
+// ReSharper disable PartialTypeWithSinglePart
+// ReSharper disable RedundantNameQualifier
+// ReSharper disable InconsistentNaming
+// ReSharper disable CheckNamespace
+// ReSharper disable UnusedParameter.Local
+// ReSharper disable RedundantUsingDirective
+#endregion
+
+namespace tests
+{
+    using System.Collections.Generic;
+
+    [global::Bond.Schema]
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public partial class Empty
+    {
+        
+        public Empty()
+        {
+            
+        }
+    }
+} // tests
diff --git a/compiler/tests/generated/constructor-parameters_init/complex_inheritance_types.cs b/compiler/tests/generated/constructor-parameters_init/complex_inheritance_types.cs
new file mode 100644
index 0000000000..496858df55
--- /dev/null
+++ b/compiler/tests/generated/constructor-parameters_init/complex_inheritance_types.cs
@@ -0,0 +1,210 @@
+
+
+// suppress "Missing XML comment for publicly visible type or member"
+#pragma warning disable 1591
+
+
+#region ReSharper warnings
+// ReSharper disable PartialTypeWithSinglePart
+// ReSharper disable RedundantNameQualifier
+// ReSharper disable InconsistentNaming
+// ReSharper disable CheckNamespace
+// ReSharper disable UnusedParameter.Local
+// ReSharper disable RedundantUsingDirective
+#endregion
+
+namespace Test
+{
+    using System.Collections.Generic;
+
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public enum TestEnum
+    {
+        EnumVal1,
+        EnumVal2,
+        EnumVal3,
+    }
+
+    [global::Bond.Schema]
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public partial class Simple
+    {
+        [global::Bond.Id(0)]
+        public int someInt { get; init; }
+
+        [global::Bond.Id(1)]
+        public int anotherInt { get; init; }
+
+        [global::Bond.Id(2), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        public string someString { get; init; }
+
+        public Simple(
+            int someInt,
+            int anotherInt,
+            string someString)
+        {
+            this.someInt = someInt;
+            this.anotherInt = anotherInt;
+            this.someString = someString;
+        }
+
+        public Simple()
+        {
+            someString = "";
+        }
+    }
+
+    [global::Bond.Schema]
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public partial class Foo
+    {
+        [global::Bond.Id(0), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        public string someText { get; init; }
+
+        public Foo(
+            string someText)
+        {
+            this.someText = someText;
+        }
+
+        public Foo()
+        {
+            someText = "BaseText1";
+        }
+    }
+
+    [global::Bond.Schema]
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public partial class Bar
+        : Foo
+    {
+        [global::Bond.Id(0)]
+        public TestEnum testEnum { get; init; }
+
+        [global::Bond.Id(1), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        new public string someText { get; init; }
+
+        [global::Bond.Id(2)]
+        public int someInt { get; init; }
+
+        [global::Bond.Id(3), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        public string moreText { get; init; }
+
+        [global::Bond.Id(4)]
+        public List<Simple> someList { get; init; }
+
+        [global::Bond.Id(5), global::Bond.Type(typeof(Dictionary<global::Bond.Tag.wstring, double>))]
+        public Dictionary<string, double> someMap { get; init; }
+
+        [global::Bond.Id(6), global::Bond.Type(typeof(HashSet<global::Bond.Tag.wstring>))]
+        public HashSet<string> someSet { get; init; }
+
+        public Bar(
+            // Base class parameters
+            string someText,
+
+            // This class parameters
+            TestEnum testEnum,
+            string someText0,
+            int someInt,
+            string moreText,
+            List<Simple> someList,
+            Dictionary<string, double> someMap,
+            HashSet<string> someSet
+        ) : base(
+                someText)
+        {
+            this.testEnum = testEnum;
+            this.someText = someText0;
+            this.someInt = someInt;
+            this.moreText = moreText;
+            this.someList = someList;
+            this.someMap = someMap;
+            this.someSet = someSet;
+        }
+
+        public Bar()
+        {
+            testEnum = TestEnum.Val2;
+            someText = "DerivedText1";
+            moreText = "";
+            someList = new List<Simple>();
+            someMap = new Dictionary<string, double>();
+            someSet = new HashSet<string>();
+        }
+    }
+
+    [global::Bond.Schema]
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public partial class Baz
+        : Bar
+    {
+        [global::Bond.Id(0), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        new public string someText { get; init; }
+
+        [global::Bond.Id(1), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        public string evenMoreText { get; init; }
+
+        [global::Bond.Id(2), global::Bond.Type(typeof(global::Bond.Tag.wstring))]
+        public string someText1 { get; init; }
+
+        public Baz(
+            // Base class parameters
+            string someText,
+            TestEnum testEnum,
+            string someText0,
+            int someInt,
+            string moreText,
+            List<Simple> someList,
+            Dictionary<string, double> someMap,
+            HashSet<string> someSet,
+
+            // This class parameters
+            string someText1,
+            string evenMoreText,
+            string someText10
+        ) : base(
+                someText,
+                testEnum,
+                someText0,
+                someInt,
+                moreText,
+                someList,
+                someMap,
+                someSet)
+        {
+            this.someText = someText1;
+            this.evenMoreText = evenMoreText;
+            this.someText1 = someText10;
+        }
+
+        public Baz()
+        {
+            someText = "";
+            evenMoreText = "";
+            someText1 = "";
+        }
+    }
+
+    [global::Bond.Schema]
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public partial class DerivedEmpty
+        : Foo
+    {
+        
+
+        public DerivedEmpty(
+            // Base class parameters
+            string someText
+        ) : base(
+                someText)
+        {
+            
+        }
+
+        public DerivedEmpty()
+        {
+            
+        }
+    }
+} // Test
diff --git a/compiler/tests/generated/constructor-parameters_init/empty_struct_types.cs b/compiler/tests/generated/constructor-parameters_init/empty_struct_types.cs
new file mode 100644
index 0000000000..eddf7b0689
--- /dev/null
+++ b/compiler/tests/generated/constructor-parameters_init/empty_struct_types.cs
@@ -0,0 +1,30 @@
+
+
+// suppress "Missing XML comment for publicly visible type or member"
+#pragma warning disable 1591
+
+
+#region ReSharper warnings
+// ReSharper disable PartialTypeWithSinglePart
+// ReSharper disable RedundantNameQualifier
+// ReSharper disable InconsistentNaming
+// ReSharper disable CheckNamespace
+// ReSharper disable UnusedParameter.Local
+// ReSharper disable RedundantUsingDirective
+#endregion
+
+namespace tests
+{
+    using System.Collections.Generic;
+
+    [global::Bond.Schema]
+    [System.CodeDom.Compiler.GeneratedCode("gbc", "0.12.1.0")]
+    public partial class Empty
+    {
+        
+        public Empty()
+        {
+            
+        }
+    }
+} // tests
diff --git a/cs/nuget/bond.csharp.test.csproj b/cs/nuget/bond.csharp.test.csproj
index 9dc0522006..1c5bd5d90b 100644
--- a/cs/nuget/bond.csharp.test.csproj
+++ b/cs/nuget/bond.csharp.test.csproj
@@ -40,4 +40,9 @@
       <Options>$(BondOptions) --using="DateTime=System.DateTime"</Options>
     </BondCodegen>
   </ItemGroup>
+  <ItemGroup Condition="$(TargetFramework.StartsWith('net5.0')) or $(TargetFramework.StartsWith('net6.0'))">
+      <BondCodegen Update="..\test\core\InitOnly.bond">
+      <Options>$(BondOptions) --init-only-properties</Options>
+    </BondCodegen>
+  </ItemGroup>
 </Project>
diff --git a/cs/test/core/SerializationTests.cs b/cs/test/core/SerializationTests.cs
index 7cae57a8b8..dc4c36a564 100644
--- a/cs/test/core/SerializationTests.cs
+++ b/cs/test/core/SerializationTests.cs
@@ -83,6 +83,20 @@ public void ReadonlySimpleContainers()
             TestSerialization<Readonly.SimpleContainers>();
         }
 
+#if NET5_0_OR_GREATER
+        [Test]
+        public void InitOnlyBasicTypes()
+        {
+            TestSerialization<InitOnly.BasicTypes>();
+        }
+
+        [Test]
+        public void InitOnlySimpleContainers()
+        {
+            TestSerialization<InitOnly.SimpleContainers>();
+        }
+#endif
+
         [Test]
         public void Nested()
         {
diff --git a/cs/test/coreNS10/CoreNS10.csproj b/cs/test/coreNS10/CoreNS10.csproj
index 1a362d6a13..4622cb7083 100644
--- a/cs/test/coreNS10/CoreNS10.csproj
+++ b/cs/test/coreNS10/CoreNS10.csproj
@@ -37,6 +37,10 @@
       <Options Condition=" '$(Configuration)' != 'Fields' ">$(BondOptions) --readonly-properties</Options>
       <Options Condition=" '$(Configuration)' == 'Fields' ">--readonly-properties --collection-interfaces</Options>
     </BondCodegen>
+    <BondCodegen Update="InitOnly.bond">
+      <Options Condition=" '$(Configuration)' != 'Fields' ">$(BondOptions) --init-only-properties</Options>
+      <Options Condition=" '$(Configuration)' == 'Fields' ">--init-only-properties --collection-interfaces</Options>
+    </BondCodegen>
     <BondCodegen Include="..\core\Containers.bond">
       <Options Condition=" '$(Configuration)' != 'Fields' ">$(BondOptions) --collection-interfaces</Options>
       <Options Condition=" '$(Configuration)' == 'Fields' ">--fields</Options>
@@ -53,6 +57,7 @@
     <Compile Include="$(IntermediateOutputPath)\NamespaceConflict_types.cs" Condition="False" />
     <Compile Include="$(IntermediateOutputPath)\NamespaceConflictBond_types.cs" Condition="False" />
     <Compile Include="$(IntermediateOutputPath)\ReadOnly_types.cs" Condition="False" />
+    <Compile Include="$(IntermediateOutputPath)\InitOnly_types.cs" Condition="False" />
     <Compile Include="$(IntermediateOutputPath)\UnitTest_types.cs" Condition="False" />
     <!-- End Resharper Workaround -->
   </ItemGroup>
diff --git a/doc/src/bond_cs.md b/doc/src/bond_cs.md
index 3c7a3a01e8..044f5bb7da 100644
--- a/doc/src/bond_cs.md
+++ b/doc/src/bond_cs.md
@@ -127,11 +127,16 @@ Schema fields are represented by properties with public getter and private
 setter and initialized to the default values in the default constructor.
 Classes with read-only properties are fully supported by all Bond APIs.
 
+`--init-only-properties`
+
+Schema fields are represented by properties with public getter and
+[C# 9 init-only setter](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/init) and initialized to the default values in the default constructor. Classes with init-only properties are fully supported by all Bond APIs.
+
 `--preview-constructor-parameters`
 
 A constructor is generated with a parameter to initialize each of the schema
 fields. This option is typically used in conjunction with
-`--readonly-properties`.  This functionailty is in preview and may change.
+`--readonly-properties` or `--init-only-properties`.  This functionailty is in preview and may change.
 
 `--collection-interfaces`