diff --git a/changelogs/fragments/deprecate_api.yml b/changelogs/fragments/deprecate_api.yml
new file mode 100644
index 00000000000..41429413ec4
--- /dev/null
+++ b/changelogs/fragments/deprecate_api.yml
@@ -0,0 +1,3 @@
+---
+deprecated_features:
+  - fact_cache - deprecate first_order_merge API (https://github.com/ansible/ansible/pull/84568).
diff --git a/lib/ansible/vars/fact_cache.py b/lib/ansible/vars/fact_cache.py
index ce0dc3a3311..d68add9d1c8 100644
--- a/lib/ansible/vars/fact_cache.py
+++ b/lib/ansible/vars/fact_cache.py
@@ -58,6 +58,10 @@ class FactCache(MutableMapping):
         self._plugin.flush()
 
     def first_order_merge(self, key, value):
+        display.deprecated(
+            "API 'first_order_merge' is deprecated, please update the usage",
+            version="2.22"
+        )
         host_facts = {key: value}
 
         try: