diff --git a/moto/sagemakerruntime/models.py b/moto/sagemakerruntime/models.py
--- a/moto/sagemakerruntime/models.py
+++ b/moto/sagemakerruntime/models.py
@@ -1,6 +1,8 @@
+import json
 from typing import Dict, List, Tuple
 
 from moto.core import BackendDict, BaseBackend
+from moto.moto_api._internal import mock_random as random
 
 
 class SageMakerRuntimeBackend(BaseBackend):
@@ -8,6 +10,7 @@ class SageMakerRuntimeBackend(BaseBackend):
 
     def __init__(self, region_name: str, account_id: str):
         super().__init__(region_name, account_id)
+        self.async_results: Dict[str, Dict[str, str]] = {}
         self.results: Dict[str, Dict[bytes, Tuple[str, str, str, str]]] = {}
         self.results_queue: List[Tuple[str, str, str, str]] = []
 
@@ -62,5 +65,37 @@ def invoke_endpoint(
             )
         return self.results[endpoint_name][unique_repr]
 
+    def invoke_endpoint_async(self, endpoint_name: str, input_location: str) -> str:
+        if endpoint_name not in self.async_results:
+            self.async_results[endpoint_name] = {}
+        if input_location in self.async_results[endpoint_name]:
+            return self.async_results[endpoint_name][input_location]
+        if self.results_queue:
+            body, _type, variant, attrs = self.results_queue.pop(0)
+        else:
+            body = "body"
+            _type = "content_type"
+            variant = "invoked_production_variant"
+            attrs = "custom_attributes"
+        json_data = {
+            "Body": body,
+            "ContentType": _type,
+            "InvokedProductionVariant": variant,
+            "CustomAttributes": attrs,
+        }
+        output = json.dumps(json_data).encode("utf-8")
+
+        output_bucket = f"sagemaker-output-{random.uuid4()}"
+        output_location = "response.json"
+        from moto.s3.models import s3_backends
+
+        s3_backend = s3_backends[self.account_id]["global"]
+        s3_backend.create_bucket(output_bucket, region_name=self.region_name)
+        s3_backend.put_object(output_bucket, output_location, value=output)
+        self.async_results[endpoint_name][
+            input_location
+        ] = f"s3://{output_bucket}/{output_location}"
+        return self.async_results[endpoint_name][input_location]
+
 
 sagemakerruntime_backends = BackendDict(SageMakerRuntimeBackend, "sagemaker-runtime")
diff --git a/moto/sagemakerruntime/responses.py b/moto/sagemakerruntime/responses.py
--- a/moto/sagemakerruntime/responses.py
+++ b/moto/sagemakerruntime/responses.py
@@ -3,6 +3,7 @@
 
 from moto.core.common_types import TYPE_RESPONSE
 from moto.core.responses import BaseResponse
+from moto.moto_api._internal import mock_random as random
 
 from .models import SageMakerRuntimeBackend, sagemakerruntime_backends
 
@@ -43,3 +44,14 @@ def invoke_endpoint(self) -> TYPE_RESPONSE:
         if custom_attributes:
             headers["X-Amzn-SageMaker-Custom-Attributes"] = custom_attributes
         return 200, headers, body
+
+    def invoke_endpoint_async(self) -> TYPE_RESPONSE:
+        endpoint_name = self.path.split("/")[2]
+        input_location = self.headers.get("X-Amzn-SageMaker-InputLocation")
+        inference_id = self.headers.get("X-Amzn-SageMaker-Inference-Id")
+        location = self.sagemakerruntime_backend.invoke_endpoint_async(
+            endpoint_name, input_location
+        )
+        resp = {"InferenceId": inference_id or str(random.uuid4())}
+        headers = {"X-Amzn-SageMaker-OutputLocation": location}
+        return 200, headers, json.dumps(resp)
diff --git a/moto/sagemakerruntime/urls.py b/moto/sagemakerruntime/urls.py
--- a/moto/sagemakerruntime/urls.py
+++ b/moto/sagemakerruntime/urls.py
@@ -10,5 +10,6 @@
 
 
 url_paths = {
+    "{0}/endpoints/(?P<name>[^/]+)/async-invocations$": response.dispatch,
     "{0}/endpoints/(?P<name>[^/]+)/invocations$": response.dispatch,
 }

diff --git a/tests/test_sagemakerruntime/test_sagemakerruntime.py b/tests/test_sagemakerruntime/test_sagemakerruntime.py
--- a/tests/test_sagemakerruntime/test_sagemakerruntime.py
+++ b/tests/test_sagemakerruntime/test_sagemakerruntime.py
@@ -1,7 +1,10 @@
+import json
+
 import boto3
 import requests
 
-from moto import mock_sagemakerruntime, settings
+from moto import mock_s3, mock_sagemakerruntime, settings
+from moto.s3.utils import bucket_and_name_from_url
 
 # See our Development Tips on writing tests for hints on how to write good tests:
 # http://docs.getmoto.org/en/latest/docs/contributing/development_tips/tests.html
@@ -54,3 +57,49 @@ def test_invoke_endpoint():
         EndpointName="asdf", Body="qwer", Accept="sth", TargetModel="tm"
     )
     assert body["Body"].read() == b"second body"
+
+
+@mock_s3
+@mock_sagemakerruntime
+def test_invoke_endpoint_async():
+    client = boto3.client("sagemaker-runtime", region_name="us-east-1")
+    base_url = (
+        "localhost:5000" if settings.TEST_SERVER_MODE else "motoapi.amazonaws.com"
+    )
+
+    sagemaker_result = {
+        "results": [
+            {
+                "Body": "first body",
+                "ContentType": "text/xml",
+                "InvokedProductionVariant": "prod",
+                "CustomAttributes": "my_attr",
+            },
+            {"Body": "second body"},
+        ]
+    }
+    requests.post(
+        f"http://{base_url}/moto-api/static/sagemaker/endpoint-results",
+        json=sagemaker_result,
+    )
+
+    # Return the first item from the list
+    body = client.invoke_endpoint_async(EndpointName="asdf", InputLocation="qwer")
+    first_output_location = body["OutputLocation"]
+
+    # Same input -> same output
+    body = client.invoke_endpoint_async(EndpointName="asdf", InputLocation="qwer")
+    assert body["OutputLocation"] == first_output_location
+
+    # Different input -> second item
+    body = client.invoke_endpoint_async(
+        EndpointName="asdf", InputLocation="asf", InferenceId="sth"
+    )
+    second_output_location = body["OutputLocation"]
+    assert body["InferenceId"] == "sth"
+
+    s3 = boto3.client("s3", "us-east-1")
+    bucket_name, obj = bucket_and_name_from_url(second_output_location)
+    resp = s3.get_object(Bucket=bucket_name, Key=obj)
+    resp = json.loads(resp["Body"].read().decode("utf-8"))
+    assert resp["Body"] == "second body"

[Enhancement] Add support for `invoke_endpoint_async` in `sagemaker-runtime`
Hi Moto team,

Thanks so much for this great library! I saw recently that you all shipped support for `sagemaker-runtime`'s `invoke_endpoint` method (https://github.com/getmoto/moto/issues/4180 and https://github.com/getmoto/moto/pull/6747). I'd like to request the addition of the `invoke-endpoint-async` method as well.

Thanks

tests/test_sagemakerruntime/test_sagemakerruntime.py::test_invoke_endpoint_async
tests/test_sagemakerruntime/test_sagemakerruntime.py::test_invoke_endpoint tests/test_sagemakerruntime/test_sagemakerruntime.py::test_invoke_endpoint__default_results