diff --git a/NEWS.md b/NEWS.md
index 0c1d4add9..55e5aa489 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -7,6 +7,8 @@
   columns to these functions will now compute the min/max/sum in each column 
   separately. Use `pl$min_horizontal()` `pl$max_horizontal()`, and 
   `pl$sum_horizontal()` instead for rowwise computation (#508).
+- `$is_not()` is deprecated and will be removed in 0.12.0. Use `$not_()` instead 
+  (#511).
 
 ## What's changed
 
diff --git a/R/expr__expr.R b/R/expr__expr.R
index a77fb7f82..0041164f0 100644
--- a/R/expr__expr.R
+++ b/R/expr__expr.R
@@ -250,18 +250,23 @@ Expr_mul = Expr_mul = function(other) {
 #' @keywords Expr Expr_operators
 #' @param other literal or Robj which can become a literal
 #' @return Exprs
-#' @usage Expr_is_not(other)
+#' @usage Expr_not_(other)
 #' @docType NULL
 #' @format NULL
 #' @examples
 #' # two syntaxes same result
-#' pl$lit(TRUE)$is_not()
+#' pl$lit(TRUE)$not_()
 #' !pl$lit(TRUE)
-Expr_is_not = "use_extendr_wrapper"
+Expr_not_ = "use_extendr_wrapper"
 #' @export
-#' @rdname Expr_is_not
+#' @rdname Expr_not_
 #' @param x Expr
-"!.Expr" = function(x) x$is_not()
+"!.Expr" = function(x) x$not_()
+
+Expr_is_not = function() {
+  warning("`$is_not()` is deprecated and will be removed in 0.12.0. Use `$not_()` instead.")
+  .pr$Expr$not_(self)
+}
 
 #' Less Than <
 #' @description lt method and operator
@@ -2173,7 +2178,7 @@ Expr_over = function(...) {
 #'     pl$lit(v)$is_unique()$alias("is_unique"),
 #'     pl$lit(v)$is_first()$alias("is_first"),
 #'     pl$lit(v)$is_duplicated()$alias("is_duplicated"),
-#'     pl$lit(v)$is_first()$is_not()$alias("R_duplicated")
+#'     pl$lit(v)$is_first()$not_()$alias("R_duplicated")
 #'   )$to_list(),
 #'   list(
 #'     is_unique = !v %in% v[duplicated(v)],
@@ -2200,7 +2205,7 @@ Expr_is_unique = "use_extendr_wrapper"
 #'     pl$lit(v)$is_unique()$alias("is_unique"),
 #'     pl$lit(v)$is_first()$alias("is_first"),
 #'     pl$lit(v)$is_duplicated()$alias("is_duplicated"),
-#'     pl$lit(v)$is_first()$is_not()$alias("R_duplicated")
+#'     pl$lit(v)$is_first()$not_()$alias("R_duplicated")
 #'   )$to_list(),
 #'   list(
 #'     is_unique = !v %in% v[duplicated(v)],
@@ -2222,7 +2227,7 @@ Expr_is_first = "use_extendr_wrapper"
 #' @name Expr_is_duplicated
 #' @format NULL
 #' @details  is_duplicated is the opposite of `is_unique()`
-#'  Looking for R like `duplicated()`?, use  `some_expr$is_first()$is_not()`
+#'  Looking for R like `duplicated()`?, use  `some_expr$is_first()$not_()`
 #'
 #' @examples
 #' v = c(1, 1, 2, 2, 3, NA, NaN, Inf)
@@ -2231,7 +2236,7 @@ Expr_is_first = "use_extendr_wrapper"
 #'     pl$lit(v)$is_unique()$alias("is_unique"),
 #'     pl$lit(v)$is_first()$alias("is_first"),
 #'     pl$lit(v)$is_duplicated()$alias("is_duplicated"),
-#'     pl$lit(v)$is_first()$is_not()$alias("R_duplicated")
+#'     pl$lit(v)$is_first()$not_()$alias("R_duplicated")
 #'   )$to_list(),
 #'   list(
 #'     is_unique = !v %in% v[duplicated(v)],
diff --git a/R/extendr-wrappers.R b/R/extendr-wrappers.R
index 9ba45b30d..a4950ba32 100644
--- a/R/extendr-wrappers.R
+++ b/R/extendr-wrappers.R
@@ -821,7 +821,7 @@ Expr$mul <- function(other) .Call(wrap__Expr__mul, self, other)
 
 Expr$div <- function(other) .Call(wrap__Expr__div, self, other)
 
-Expr$is_not <- function() .Call(wrap__Expr__is_not, self)
+Expr$not_ <- function() .Call(wrap__Expr__not_, self)
 
 Expr$over <- function(proto_exprs) .Call(wrap__Expr__over, self, proto_exprs)
 
diff --git a/man/Expr_is_duplicated.Rd b/man/Expr_is_duplicated.Rd
index a913c8c53..65831922c 100644
--- a/man/Expr_is_duplicated.Rd
+++ b/man/Expr_is_duplicated.Rd
@@ -15,7 +15,7 @@ Get mask of duplicated values.
 }
 \details{
 is_duplicated is the opposite of \code{is_unique()}
-Looking for R like \code{duplicated()}?, use  \code{some_expr$is_first()$is_not()}
+Looking for R like \code{duplicated()}?, use  \code{some_expr$is_first()$not_()}
 }
 \examples{
 v = c(1, 1, 2, 2, 3, NA, NaN, Inf)
@@ -24,7 +24,7 @@ all.equal(
     pl$lit(v)$is_unique()$alias("is_unique"),
     pl$lit(v)$is_first()$alias("is_first"),
     pl$lit(v)$is_duplicated()$alias("is_duplicated"),
-    pl$lit(v)$is_first()$is_not()$alias("R_duplicated")
+    pl$lit(v)$is_first()$not_()$alias("R_duplicated")
   )$to_list(),
   list(
     is_unique = !v \%in\% v[duplicated(v)],
diff --git a/man/Expr_is_first.Rd b/man/Expr_is_first.Rd
index e67b578fd..782110edb 100644
--- a/man/Expr_is_first.Rd
+++ b/man/Expr_is_first.Rd
@@ -19,7 +19,7 @@ all.equal(
     pl$lit(v)$is_unique()$alias("is_unique"),
     pl$lit(v)$is_first()$alias("is_first"),
     pl$lit(v)$is_duplicated()$alias("is_duplicated"),
-    pl$lit(v)$is_first()$is_not()$alias("R_duplicated")
+    pl$lit(v)$is_first()$not_()$alias("R_duplicated")
   )$to_list(),
   list(
     is_unique = !v \%in\% v[duplicated(v)],
diff --git a/man/Expr_is_unique.Rd b/man/Expr_is_unique.Rd
index 0e7ab1304..c28fb715a 100644
--- a/man/Expr_is_unique.Rd
+++ b/man/Expr_is_unique.Rd
@@ -19,7 +19,7 @@ all.equal(
     pl$lit(v)$is_unique()$alias("is_unique"),
     pl$lit(v)$is_first()$alias("is_first"),
     pl$lit(v)$is_duplicated()$alias("is_duplicated"),
-    pl$lit(v)$is_first()$is_not()$alias("R_duplicated")
+    pl$lit(v)$is_first()$not_()$alias("R_duplicated")
   )$to_list(),
   list(
     is_unique = !v \%in\% v[duplicated(v)],
diff --git a/man/Expr_is_not.Rd b/man/Expr_not_.Rd
similarity index 82%
rename from man/Expr_is_not.Rd
rename to man/Expr_not_.Rd
index 781915b08..45795d536 100644
--- a/man/Expr_is_not.Rd
+++ b/man/Expr_not_.Rd
@@ -1,11 +1,11 @@
 % Generated by roxygen2: do not edit by hand
 % Please edit documentation in R/expr__expr.R
-\name{Expr_is_not}
-\alias{Expr_is_not}
+\name{Expr_not_}
+\alias{Expr_not_}
 \alias{!.Expr}
 \title{Not !}
 \usage{
-Expr_is_not(other)
+Expr_not_(other)
 
 \method{!}{Expr}(x)
 }
@@ -22,7 +22,7 @@ not method and operator
 }
 \examples{
 # two syntaxes same result
-pl$lit(TRUE)$is_not()
+pl$lit(TRUE)$not_()
 !pl$lit(TRUE)
 }
 \keyword{Expr}
diff --git a/src/rust/src/lazy/dsl.rs b/src/rust/src/lazy/dsl.rs
index 0a6d982b3..d5f84368d 100644
--- a/src/rust/src/lazy/dsl.rs
+++ b/src/rust/src/lazy/dsl.rs
@@ -1660,7 +1660,7 @@ impl Expr {
     }
 
     //unary
-    pub fn is_not(&self) -> Self {
+    pub fn not_(&self) -> Self {
         self.0.clone().not().into()
     }
 
diff --git a/tests/testthat/test-expr.R b/tests/testthat/test-expr.R
index 896514df6..86971ec1e 100644
--- a/tests/testthat/test-expr.R
+++ b/tests/testthat/test-expr.R
@@ -13,20 +13,20 @@ test_that("expression boolean operators", {
 
   cmp_operators_df = pl$DataFrame(list())$with_columns(
     (pl$lit(1) < 2)$alias("1 lt 2"),
-    (pl$lit(1) < 1)$alias("1 lt 1 not")$is_not(),
+    (pl$lit(1) < 1)$alias("1 lt 1 not")$not_(),
     (pl$lit(2) > 1)$alias("2 gt 1"),
-    (pl$lit(1) > 1)$alias("1 gt 1 not")$is_not(),
+    (pl$lit(1) > 1)$alias("1 gt 1 not")$not_(),
     (pl$lit(1) == 1)$alias("1 eq 1"),
-    (pl$lit(1) == 2)$alias("1 eq 2 not")$is_not(),
+    (pl$lit(1) == 2)$alias("1 eq 2 not")$not_(),
     (pl$lit(1) <= 1)$alias("1 lt_eq 1"),
-    (pl$lit(2) <= 1)$alias("2 lt_eq 1 not")$is_not(),
+    (pl$lit(2) <= 1)$alias("2 lt_eq 1 not")$not_(),
     (pl$lit(2) >= 2)$alias("2 gt_eq 2"),
-    (pl$lit(1) >= 2)$alias("1 gt_eq 2 not")$is_not(),
+    (pl$lit(1) >= 2)$alias("1 gt_eq 2 not")$not_(),
     (pl$lit(2) != 1)$alias("2 not eq 1"),
-    (pl$lit(2) != 2)$alias("2 not eq 1 not")$is_not(),
-    (pl$lit(TRUE)$is_not() == pl$lit(FALSE))$alias("not true == false"),
+    (pl$lit(2) != 2)$alias("2 not eq 1 not")$not_(),
+    (pl$lit(TRUE)$not_() == pl$lit(FALSE))$alias("not true == false"),
     (pl$lit(TRUE) != pl$lit(FALSE))$alias("true != false"),
-    (pl$lit(TRUE)$is_not() == FALSE)$alias("not true == false wrap"),
+    (pl$lit(TRUE)$not_() == FALSE)$alias("not true == false wrap"),
     (pl$lit(TRUE) != FALSE)$alias("true != false wrap")
   )
 
@@ -248,7 +248,7 @@ test_that("is_null", {
 
   expect_equal(
     df$with_columns(pl$all()$is_not_null()$name$suffix("_isnull"))$to_data_frame(),
-    df$with_columns(pl$all()$is_null()$is_not()$name$suffix("_isnull"))$to_data_frame()
+    df$with_columns(pl$all()$is_null()$not_()$name$suffix("_isnull"))$to_data_frame()
   )
 })
 
@@ -466,7 +466,7 @@ test_that("and or is_in xor", {
       pl$lit(NA_real_)$is_in(pl$lit(NULL))$alias("NULL typed is in NULL")
 
       # anymore from rust-polars 0.30-0.32
-      # pl$lit(NULL)$is_in(pl$lit(NULL))$is_not()$alias("NULL is in NULL, NOY")
+      # pl$lit(NULL)$is_in(pl$lit(NULL))$not_()$alias("NULL is in NULL, NOY")
     )$to_data_frame() |> unlist() |> all(na.rm = TRUE)
   )
 })
@@ -1269,7 +1269,7 @@ test_that("is_unique is_first is_duplicated", {
       pl$lit(v)$is_unique()$alias("is_unique"),
       pl$lit(v)$is_first()$alias("is_first"),
       pl$lit(v)$is_duplicated()$alias("is_duplicated"),
-      pl$lit(v)$is_first()$is_not()$alias("R_duplicated")
+      pl$lit(v)$is_first()$not_()$alias("R_duplicated")
     )$to_list(),
     list(
       is_unique = !v %in% v[duplicated(v)],