diff --git a/src/aggregations/metrics-aggregations/index.js b/src/aggregations/metrics-aggregations/index.js
index 79a3b391..c30b1b30 100644
--- a/src/aggregations/metrics-aggregations/index.js
+++ b/src/aggregations/metrics-aggregations/index.js
@@ -16,3 +16,4 @@ exports.StatsAggregation = require('./stats-aggregation');
 exports.SumAggregation = require('./sum-aggregation');
 exports.TopHitsAggregation = require('./top-hits-aggregation');
 exports.ValueCountAggregation = require('./value-count-aggregation');
+exports.WeightedAverageAggregation = require('./weighted-average-aggregation');
diff --git a/src/aggregations/metrics-aggregations/metrics-aggregation-base.js b/src/aggregations/metrics-aggregations/metrics-aggregation-base.js
index 9d4924cf..ca84dd47 100644
--- a/src/aggregations/metrics-aggregations/metrics-aggregation-base.js
+++ b/src/aggregations/metrics-aggregations/metrics-aggregation-base.js
@@ -75,7 +75,7 @@ class MetricsAggregationBase extends Aggregation {
     }
 
     /**
-     * Sets the missing parameter ehich defines how documents
+     * Sets the missing parameter which defines how documents
      * that are missing a value should be treated.
      *
      * @example
diff --git a/src/aggregations/metrics-aggregations/weighted-average-aggregation.js b/src/aggregations/metrics-aggregations/weighted-average-aggregation.js
new file mode 100644
index 00000000..51a1ffc7
--- /dev/null
+++ b/src/aggregations/metrics-aggregations/weighted-average-aggregation.js
@@ -0,0 +1,171 @@
+'use strict';
+
+const { Script } = require('../../core');
+const MetricsAggregationBase = require('./metrics-aggregation-base');
+const isNil = require('lodash.isnil');
+
+const ES_REF_URL =
+    'https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-metrics-weight-avg-aggregation.html';
+
+/**
+ * A single-value metrics aggregation that computes the weighted average of numeric values that are extracted from the aggregated documents.
+ * These values can be extracted either from specific numeric fields in the documents.
+ *
+ * [Elasticsearch reference](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-metrics-weight-avg-aggregation.html)
+ *
+ * Added in Elasticsearch v6.4.0
+ * [Release notes](https://www.elastic.co/guide/en/elasticsearch/reference/6.4/release-notes-6.4.0.html)
+ *
+ * As a formula, a weighted average is ∑(value * weight) / ∑(weight)
+ *
+ * @example
+ * // Compute the average grade over all documents, weighing by teacher score.
+ * const agg = esb.weightedAverageAggregation('avg_grade', 'grade', 'teacher_score');
+ *
+ * @example
+ * // Compute the average grade where the weight is calculated by a script.
+ * // Filling in missing values as '10'.
+ * const agg = esb.weightedAverageAggregation('avg_grade', 'grade')
+ *      .weight(esb.script('inline', "doc['teacher_score'].value").lang('painless'), 10)
+ * );
+ *
+ * @example
+ * // Compute the average grade, weighted by teacher score, filling in missing values.
+ * const agg = esb.weightedAverageAggregation('avg_grade').value('grade', 5).weight('teacher_score', 10));
+ *
+ * @example
+ * // Compute the average grade over all documents, weighing by teacher score.
+ * const agg = esb.weightedAverageAggregation('avg_grade').value('grade').weight('teacher_score');
+ *
+ *
+ * @param {string} name The name which will be used to refer to this aggregation.
+ * @param {string=} value The field or script to use as the value
+ * @param {string=} weight The field or script to use as the weight
+ *
+ * @extends MetricsAggregationBase
+ */
+class WeightedAverageAggregation extends MetricsAggregationBase {
+    /**
+     * Creates an instance of `WeightedAverageAggregation`
+     *
+     * @param {string} name The name which will be used to refer to this aggregation.
+     * @param {string=} value The field or script to be used as the value.
+     * @param {string=} weight The field or script to be used as the weighting.
+     */
+    constructor(name, value, weight) {
+        super(name, 'weighted_avg');
+
+        this._aggsDef.value = {};
+        this._aggsDef.weight = {};
+
+        if (!isNil(value)) {
+            this.value(value);
+        }
+
+        if (!isNil(weight)) {
+            this.weight(weight);
+        }
+    }
+
+    /**
+     * Sets the value
+     *
+     * @param {string | Script} value Field name or script to use as the value.
+     *
+     * @param {number=} missing Sets the missing parameter which defines how documents
+     * that are missing a value should be treated.
+     * @returns {WeightedAverageAggregation} returns `this` so that calls can be chained
+     */
+    value(value, missing) {
+        if (typeof value !== 'string' && !(value instanceof Script)) {
+            throw new TypeError(
+                'Value must be either a string or instanceof Script'
+            );
+        }
+
+        if (value instanceof Script) {
+            if (this._aggsDef.value.field) {
+                delete this._aggsDef.value.field;
+            }
+            this._aggsDef.value.script = value;
+        } else {
+            if (this._aggsDef.value.script) {
+                delete this._aggsDef.value.script;
+            }
+            this._aggsDef.value.field = value;
+        }
+
+        if (!isNil(missing)) {
+            this._aggsDef.value.missing = missing;
+        }
+
+        return this;
+    }
+
+    /**
+     * Sets the weight
+     *
+     * @param {string | Script} weight Field name or script to use as the weight.
+     * @param {number=} missing Sets the missing parameter which defines how documents
+     * that are missing a value should be treated.
+     * @returns {WeightedAverageAggregation} returns `this` so that calls can be chained
+     */
+    weight(weight, missing) {
+        if (typeof weight !== 'string' && !(weight instanceof Script)) {
+            throw new TypeError(
+                'Weight must be either a string or instanceof Script'
+            );
+        }
+
+        if (weight instanceof Script) {
+            if (this._aggsDef.weight.field) {
+                delete this._aggsDef.weight.field;
+            }
+            this._aggsDef.weight.script = weight;
+        } else {
+            if (this._aggsDef.weight.script) {
+                delete this._aggsDef.weight.script;
+            }
+            this._aggsDef.weight.field = weight;
+        }
+
+        if (!isNil(missing)) {
+            this._aggsDef.weight.missing = missing;
+        }
+
+        return this;
+    }
+
+    /**
+     * @override
+     * @throws {Error} This method cannot be called on WeightedAverageAggregation
+     */
+    script() {
+        console.log(`Please refer ${ES_REF_URL}`);
+        throw new Error(
+            'script is not supported in WeightedAverageAggregation'
+        );
+    }
+
+    /**
+     * @override
+     * @throws {Error} This method cannot be called on WeightedAverageAggregation
+     */
+    missing() {
+        console.log(`Please refer ${ES_REF_URL}`);
+        throw new Error(
+            'missing is not supported in WeightedAverageAggregation'
+        );
+    }
+
+    /**
+     * @override
+     * @throws {Error} This method cannot be called on WeightedAverageAggregation
+     */
+    field() {
+        console.log(`Please refer ${ES_REF_URL}`);
+        throw new Error('field is not supported in WeightedAverageAggregation');
+    }
+}
+
+module.exports = WeightedAverageAggregation;
diff --git a/src/index.d.ts b/src/index.d.ts
index db3b6740..606d1d49 100644
--- a/src/index.d.ts
+++ b/src/index.d.ts
@@ -3843,6 +3843,81 @@ declare namespace esb {
         field?: string
     ): AvgAggregation;
 
+    /**
+     * A single-value metrics aggregation that computes the weighted average of numeric values that are extracted from the aggregated documents.
+     * These values can be extracted either from specific numeric fields in the documents.
+     * 
+     * [Elasticsearch reference](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-metrics-weight-avg-aggregation.html)
+     * 
+     * Added in Elasticsearch v6.4.0
+     * [Release notes](https://www.elastic.co/guide/en/elasticsearch/reference/6.4/release-notes-6.4.0.html)
+     *
+     * @param {string} name The name which will be used to refer to this aggregation.
+     * @param {string=} value The field or script to be used as the value.
+     * @param {string | Script =} weight The field or script to be used as the weighting.
+     * @extends MetricsAggregationBase
+     */
+    export class WeightedAverageAggregation extends MetricsAggregationBase {
+        constructor(name: string, value?: string | Script, weight?: string | Script);
+
+        /**
+         * Sets the value
+         * 
+         * @param {string | Script} value Field name or script to be used as the value
+         * @param {number=} missing Sets the missing parameter which defines how documents
+         * that are missing a value should be treated.
+         * @return {WeightedAverageAggregation} returns `this` so that calls can be chained
+         */
+        value(value: string | Script, missing?: number): WeightedAverageAggregation
+
+        /**
+         * Sets the weight
+         * 
+         * @param {string | Script} weight Field name or script to be used as the weight
+         * @param {number=} missing Sets the missing parameter which defines how documents
+         * that are missing a value should be treated.
+         * @return {WeightedAverageAggregation} returns `this` so that calls can be chained
+         */
+        weight(weight: string | Script, missing?: number): WeightedAverageAggregation
+
+        /**
+        * @override
+        * @throws {Error} This method cannot be called on WeightedAverageAggregation
+        */
+        script(): never;
+
+        /**
+        * @override
+        * @throws {Error} This method cannot be called on WeightedAverageAggregation
+        */
+        missing(): never;
+
+        /**
+        * @override
+        * @throws {Error} This method cannot be called on WeightedAverageAggregation
+        */
+        field(): never;
+    }
+
+    /**
+     * A single-value metrics aggregation that computes the weighted average of numeric values that are extracted from the aggregated documents.
+     * These values can be extracted either from specific numeric fields in the documents.
+     * 
+     * [Elasticsearch reference](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-metrics-weight-avg-aggregation.html)
+     * 
+     * Added in Elasticsearch v6.4.0
+     * [Release notes](https://www.elastic.co/guide/en/elasticsearch/reference/6.4/release-notes-6.4.0.html)
+     *
+     * @param {string} name The name which will be used to refer to this aggregation.
+     * @param {string | Script =} value The field or script to be used as the value.
+     * @param {string | Script =} weight The field or script to be used as the weighting.
+     */
+    export function weightedAverageAggregation(
+        name: string,
+        value?: string | Script,
+        weight?: string | Script
+    ): WeightedAverageAggregation;
+
     /**
      * A single-value metrics aggregation that calculates an approximate count of
      * distinct values. Values can be extracted either from specific fields in the
diff --git a/src/index.js b/src/index.js
index 2d1bf63f..6a45a593 100644
--- a/src/index.js
+++ b/src/index.js
@@ -105,7 +105,8 @@ const {
         StatsAggregation,
         SumAggregation,
         TopHitsAggregation,
-        ValueCountAggregation
+        ValueCountAggregation,
+        WeightedAverageAggregation
     },
     bucketAggregations: {
         AdjacencyMatrixAggregation,
@@ -347,6 +348,11 @@ exports.spanFieldMaskingQuery = constructorWrapper(SpanFieldMaskingQuery);
 exports.AvgAggregation = AvgAggregation;
 exports.avgAggregation = constructorWrapper(AvgAggregation);
 
+exports.WeightedAverageAggregation = WeightedAverageAggregation;
+exports.weightedAverageAggregation = constructorWrapper(
+    WeightedAverageAggregation
+);
+
 exports.CardinalityAggregation = CardinalityAggregation;
 exports.cardinalityAggregation = constructorWrapper(CardinalityAggregation);
 
diff --git a/test/aggregations-test/weighted-average-aggregation.test.js b/test/aggregations-test/weighted-average-aggregation.test.js
new file mode 100644
index 00000000..555fe55c
--- /dev/null
+++ b/test/aggregations-test/weighted-average-aggregation.test.js
@@ -0,0 +1,206 @@
+import test from 'ava';
+import { WeightedAverageAggregation, Script } from '../../src';
+import {
+    illegalCall,
+    makeSetsOptionMacro,
+    nameTypeExpectStrategy,
+    setsAggType
+} from '../_macros';
+
+test(setsAggType, WeightedAverageAggregation, 'weighted_avg', {
+    value: {},
+    weight: {}
+});
+
+const getInstance = (...args) =>
+    new WeightedAverageAggregation('my_agg', ...args);
+
+const setsOption = makeSetsOptionMacro(
+    getInstance,
+    nameTypeExpectStrategy('my_agg', 'weighted_avg', { value: {}, weight: {} })
+);
+test(illegalCall, WeightedAverageAggregation, 'field', 'my_agg');
+test(illegalCall, WeightedAverageAggregation, 'script', 'my_agg');
+test(illegalCall, WeightedAverageAggregation, 'missing', 'my_agg');
+
+test(setsOption, 'weight', {
+    param: 'my_weight_field',
+    propValue: { field: 'my_weight_field' }
+});
+test(setsOption, 'value', {
+    param: 'my_value_field',
+    propValue: { field: 'my_value_field' }
+});
+
+test(setsOption, 'weight', {
+    param: ['my_weight_field', 20],
+    spread: true,
+    propValue: { field: 'my_weight_field', missing: 20 }
+});
+test(setsOption, 'value', {
+    param: ['my_value_field', 10],
+    spread: true,
+    propValue: { field: 'my_value_field', missing: 10 }
+});
+
+test(setsOption, 'value', {
+    param: new Script('inline', "doc['field'].value"),
+    propValue: { script: { inline: "doc['field'].value" } }
+});
+test(setsOption, 'weight', {
+    param: new Script('inline', "doc['field'].value"),
+    propValue: { script: { inline: "doc['field'].value" } }
+});
+
+test('throws if value is not a script or string', t => {
+    const error = t.throws(
+        () => new WeightedAverageAggregation('my_agg').value(10, 10),
+        TypeError
+    );
+    t.is(error.message, 'Value must be either a string or instanceof Script');
+});
+
+test('throws if weight is not a script or string', t => {
+    const error = t.throws(
+        () => new WeightedAverageAggregation('my_agg').weight(10, 10),
+        TypeError
+    );
+    t.is(error.message, 'Weight must be either a string or instanceof Script');
+});
+
+test('removes previously set value field/script when updated', t => {
+    const valueOne = new WeightedAverageAggregation('my_agg').value(
+        new Script('inline', 'script')
+    );
+    const expectedOne = {
+        my_agg: {
+            weighted_avg: {
+                value: {
+                    script: {
+                        inline: 'script'
+                    }
+                },
+                weight: {}
+            }
+        }
+    };
+    t.deepEqual(valueOne.toJSON(), expectedOne);
+    const valueTwo = valueOne.value('my_field');
+    const expectedTwo = {
+        my_agg: {
+            weighted_avg: {
+                value: {
+                    field: 'my_field'
+                },
+                weight: {}
+            }
+        }
+    };
+    t.deepEqual(valueTwo.toJSON(), expectedTwo);
+    const valueThree = valueOne.value(new Script('inline', 'script2'));
+    const expectedThree = {
+        my_agg: {
+            weighted_avg: {
+                value: {
+                    script: {
+                        inline: 'script2'
+                    }
+                },
+                weight: {}
+            }
+        }
+    };
+    t.deepEqual(valueThree.toJSON(), expectedThree);
+});
+
+test('removes previously set weight field/script when updated', t => {
+    const valueOne = new WeightedAverageAggregation('my_agg').weight(
+        new Script('inline', 'script')
+    );
+    const expectedOne = {
+        my_agg: {
+            weighted_avg: {
+                weight: {
+                    script: {
+                        inline: 'script'
+                    }
+                },
+                value: {}
+            }
+        }
+    };
+    t.deepEqual(valueOne.toJSON(), expectedOne);
+    const valueTwo = valueOne.weight('my_field');
+    const expectedTwo = {
+        my_agg: {
+            weighted_avg: {
+                weight: {
+                    field: 'my_field'
+                },
+                value: {}
+            }
+        }
+    };
+    t.deepEqual(valueTwo.toJSON(), expectedTwo);
+    const valueThree = valueOne.weight(new Script('inline', 'script2'));
+    const expectedThree = {
+        my_agg: {
+            weighted_avg: {
+                weight: {
+                    script: {
+                        inline: 'script2'
+                    }
+                },
+                value: {}
+            }
+        }
+    };
+    t.deepEqual(valueThree.toJSON(), expectedThree);
+});
+
+test('constructor sets value and weight', t => {
+    const value = new WeightedAverageAggregation(
+        'my_agg',
+        'my_value',
+        'my_weight'
+    ).toJSON();
+    const expected = {
+        my_agg: {
+            weighted_avg: {
+                value: {
+                    field: 'my_value'
+                },
+                weight: {
+                    field: 'my_weight'
+                }
+            }
+        }
+    };
+    t.deepEqual(value, expected);
+});
+
+test('constructor sets value and weight as scripts', t => {
+    const getScript = arg => new Script('inline', `doc['${arg}'].value`);
+    const value = new WeightedAverageAggregation(
+        'my_agg',
+        getScript('value'),
+        getScript('weight')
+    ).toJSON();
+    const expected = {
+        my_agg: {
+            weighted_avg: {
+                value: {
+                    script: {
+                        inline: "doc['value'].value"
+                    }
+                },
+                weight: {
+                    script: {
+                        inline: "doc['weight'].value"
+                    }
+                }
+            }
+        }
+    };
+    t.deepEqual(value, expected);
+});