diff --git a/docs/changelog/118104.yaml b/docs/changelog/118104.yaml
index 4141d9da5c033..7f7861846e231 100644
--- a/docs/changelog/118104.yaml
+++ b/docs/changelog/118104.yaml
@@ -6,7 +6,7 @@ issues: []
 breaking:
   title: Remove old `_knn_search` tech preview API in v9
   area: Vector Search
-  details: Please describe the details of this change for the release notes. You can
-    use asciidoc.
-  impact: Please describe the impact of this change to users
+  details: The original, tech-preview api for vector search, `_knn_search`, has been removed in v9. For all vector search
+    operations, you should utilize the `_search` endpoint.
+  impact: The `_knn_search` API is now inaccessible without providing a compatible-with flag for v8.
   notable: false
diff --git a/docs/reference/mapping/types/dense-vector.asciidoc b/docs/reference/mapping/types/dense-vector.asciidoc
index e6e11d6dd539f..199a59a5b143c 100644
--- a/docs/reference/mapping/types/dense-vector.asciidoc
+++ b/docs/reference/mapping/types/dense-vector.asciidoc
@@ -232,8 +232,8 @@ it will be set to the length of the first vector added to the field.
 
 `index`::
 (Optional, Boolean)
-If `true`, you can search this field using the <<knn-search-api, kNN search
-API>>. Defaults to `true`.
+If `true`, you can search this field using the <<query-dsl-knn-query, knn query>>
+or <<search-api-knn, knn in _search>> . Defaults to `true`.
 
 [[dense-vector-similarity]]
 `similarity`::
diff --git a/docs/reference/search.asciidoc b/docs/reference/search.asciidoc
index b39afff876eed..70ffe02e44d95 100644
--- a/docs/reference/search.asciidoc
+++ b/docs/reference/search.asciidoc
@@ -50,8 +50,6 @@ include::search/async-search.asciidoc[]
 
 include::search/point-in-time-api.asciidoc[]
 
-include::search/knn-search.asciidoc[]
-
 include::search/retriever.asciidoc[]
 
 include::search/rrf.asciidoc[]
diff --git a/docs/reference/search/knn-search.asciidoc b/docs/reference/search/knn-search.asciidoc
deleted file mode 100644
index 78e3e13b09fee..0000000000000
--- a/docs/reference/search/knn-search.asciidoc
+++ /dev/null
@@ -1,146 +0,0 @@
-[[knn-search-api]]
-=== kNN search API
-++++
-<titleabbrev>kNN search</titleabbrev>
-++++
-
-deprecated::[8.4.0,"The kNN search API has been replaced by the <<search-api-knn, `knn` option>> in the search API."]
-
-Performs a k-nearest neighbor (kNN) search and returns the matching documents.
-
-////
-[source,console]
-----
-PUT my-index
-{
-  "mappings": {
-    "properties": {
-      "image_vector": {
-        "type": "dense_vector",
-        "dims": 3,
-        "index": true,
-        "similarity": "l2_norm"
-      }
-    }
-  }
-}
-
-PUT my-index/_doc/1?refresh
-{
-  "image_vector" : [0.5, 10, 6]
-}
-----
-////
-
-[source,console]
-----
-GET my-index/_knn_search
-{
-  "knn": {
-    "field": "image_vector",
-    "query_vector": [0.3, 0.1, 1.2],
-    "k": 10,
-    "num_candidates": 100
-  },
-  "_source": ["name", "file_type"]
-}
-----
-// TEST[continued]
-// TEST[warning:The kNN search API has been replaced by the `knn` option in the search API.]
-
-[[knn-search-api-request]]
-==== {api-request-title}
-
-`GET <target>/_knn_search`
-
-`POST <target>/_knn_search`
-
-[[knn-search-api-prereqs]]
-==== {api-prereq-title}
-
-* If the {es} {security-features} are enabled, you must have the `read`
-<<privileges-list-indices,index privilege>> for the target data stream, index,
-or alias.
-
-[[knn-search-api-desc]]
-==== {api-description-title}
-
-The kNN search API performs a k-nearest neighbor (kNN) search on a
-<<dense-vector,`dense_vector`>> field. Given a query vector, it finds the _k_
-closest vectors and returns those documents as search hits.
-
-//tag::hnsw-algorithm[]
-{es} uses the https://arxiv.org/abs/1603.09320[HNSW algorithm] to support
-efficient kNN search. Like most kNN algorithms, HNSW is an approximate method
-that sacrifices result accuracy for improved search speed. This means the
-results returned are not always the true _k_ closest neighbors.
-//end::hnsw-algorithm[]
-
-The kNN search API supports restricting the search using a filter. The search
-will return the top `k` documents that also match the filter query.
-
-[[knn-search-api-path-params]]
-==== {api-path-parms-title}
-
-`<target>`::
-(Optional, string) Comma-separated list of data streams, indices, and aliases
-to search. Supports wildcards (`*`). To search all data streams and indices,
-use `*` or `_all`.
-
-[role="child_attributes"]
-[[knn-search-api-query-params]]
-==== {api-query-parms-title}
-
-include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=routing]
-
-[role="child_attributes"]
-[[knn-search-api-request-body]]
-==== {api-request-body-title}
-
-`filter`::
-(Optional, <<query-dsl,Query DSL object>>)
-include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=knn-filter]
-
-`knn`::
-(Required, object)
-include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=knn]
-+
-.Properties of `knn` object
-[%collapsible%open]
-====
-`field`::
-(Required, string)
-include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=knn-field]
-
-`k`::
-(Optional, integer)
-include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=knn-k]
-
-`num_candidates`::
-(Optional, integer)
-include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=knn-num-candidates]
-
-`query_vector`::
-(Required, array of floats or string)
-include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=knn-query-vector]
-====
-
-include::{es-ref-dir}/search/search.asciidoc[tag=docvalue-fields-def]
-include::{es-ref-dir}/search/search.asciidoc[tag=fields-param-def]
-include::{es-ref-dir}/search/search.asciidoc[tag=source-filtering-def]
-include::{es-ref-dir}/search/search.asciidoc[tag=stored-fields-def]
-
-[role="child_attributes"]
-[[knn-search-api-response-body]]
-==== {api-response-body-title}
-
-A kNN search response has the exact same structure as a
-<<search-api-response-body, search API response>>. However, certain sections
-have a meaning specific to kNN search:
-
-* The <<search-api-response-body-score,document `_score`>> is determined by
-the similarity between the query and document vector. See
-<<dense-vector-similarity, `similarity`>>.
-* The `hits.total` object contains the total number of nearest neighbor
-candidates considered, which is `num_candidates * num_shards`. The
-`hits.total.relation` will always be `eq`, indicating an exact value.
diff --git a/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/40_knn_search.yml b/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/40_knn_search.yml
index 272db8ba03dcc..78a86e4026b30 100644
--- a/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/40_knn_search.yml
+++ b/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/40_knn_search.yml
@@ -215,7 +215,7 @@ setup:
 ---
 "kNN search in _knn_search endpoint":
   - skip:
-      features: [ "allowed_warnings" ]
+      features: [ "allowed_warnings", "headers" ]
   - do:
       headers:
         Content-Type: "application/vnd.elasticsearch+json;compatible-with=8"
@@ -243,7 +243,7 @@ setup:
   - requires:
       cluster_features: "gte_v8.2.0"
       reason: 'kNN with filtering added in 8.2'
-      test_runner_features: [ "allowed_warnings" ]
+      test_runner_features: [ "allowed_warnings", "headers" ]
   - do:
       headers:
         Content-Type: "application/vnd.elasticsearch+json;compatible-with=8"