diff --git a/CHANGES.md b/CHANGES.md
index a4887a6..90cd342 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -22,7 +22,11 @@ To be released.
      -  The default `rules` for `kvCache()` function are now 5 minutes for all
         URLs.
 
+ -  Added `Offer` class to Activity Vocabulary API.
+    [[#65], [#76]]
+
 [#74]: https://github.com/dahlia/fedify/issues/74
+[#76]: https://github.com/dahlia/fedify/pull/76
 
 
 Version 0.10.0
diff --git a/vocab/offer.yaml b/vocab/offer.yaml
new file mode 100644
index 0000000..1d0b04f
--- /dev/null
+++ b/vocab/offer.yaml
@@ -0,0 +1,13 @@
+$schema: ../codegen/schema.yaml
+name: Offer
+uri: "https://www.w3.org/ns/activitystreams#Offer"
+extends: "https://www.w3.org/ns/activitystreams#Activity"
+entity: true
+description: |
+  Indicates that the actor is offering the object.
+  If specified, the target indicates the entity to which
+  the object is being offered.
+defaultContext:
+- "https://www.w3.org/ns/activitystreams"
+- "https://w3id.org/security/data-integrity/v1"
+properties: []