diff --git a/openapi/openapiv2.json b/openapi/openapiv2.json
index 7ab6e24cc..1c8f7689e 100644
--- a/openapi/openapiv2.json
+++ b/openapi/openapiv2.json
@@ -7633,6 +7633,17 @@
         }
       }
     },
+    "PayloadExternalReference": {
+      "type": "object",
+      "properties": {
+        "sizeBytes": {
+          "type": "string",
+          "format": "int64",
+          "title": "Size in bytes of the externally stored object"
+        }
+      },
+      "description": "Describes an externally stored object referenced by this Payload."
+    },
     "PendingActivityInfoPauseInfo": {
       "type": "object",
       "properties": {
diff --git a/openapi/openapiv3.yaml b/openapi/openapiv3.yaml
index d26d110de..7eeaf410c 100644
--- a/openapi/openapiv3.yaml
+++ b/openapi/openapiv3.yaml
@@ -9790,6 +9790,13 @@ components:
         Represents some binary (byte array) data (ex: activity input parameters or workflow result) with
          metadata which describes this binary data (format, encoding, encryption, etc). Serialization
          of the data may be user-defined.
+    Payload_ExternalReference:
+      type: object
+      properties:
+        sizeBytes:
+          type: string
+          description: Size in bytes of the externally stored object
+      description: Describes an externally stored object referenced by this Payload.
     Payloads:
       type: object
       properties:
diff --git a/temporal/api/common/v1/message.proto b/temporal/api/common/v1/message.proto
index 838f5fefc..b77c413cd 100644
--- a/temporal/api/common/v1/message.proto
+++ b/temporal/api/common/v1/message.proto
@@ -32,8 +32,18 @@ message Payloads {
 message Payload {
     map<string,bytes> metadata = 1;
     bytes data = 2;
+    // References to data stored externally rather than embedded in the payload.
+    // A Payload can reference zero or more external objects.
+    repeated ExternalReference external_references = 3;
+
+    // Describes an externally stored object referenced by this Payload.
+    message ExternalReference {
+        // Size in bytes of the externally stored object
+        int64 size_bytes = 1;
+    }
 }
 
+
 // A user-defined set of *indexed* fields that are used/exposed when listing/searching workflows.
 // The payload is not serialized in a user-defined way.
 message SearchAttributes {