diff --git a/src/gha_runner/clouddeployment.py b/src/gha_runner/clouddeployment.py
index edfa945..7f04c39 100644
--- a/src/gha_runner/clouddeployment.py
+++ b/src/gha_runner/clouddeployment.py
@@ -1,9 +1,13 @@
+import importlib.resources
+import os
 from abc import ABC, abstractmethod
-from gha_runner.gh import GitHubInstance
 from dataclasses import dataclass, field
-import importlib.resources
-import boto3
 from string import Template
+from typing import Optional
+
+import boto3
+
+from gha_runner.gh import GitHubInstance
 
 
 class CloudDeployment(ABC):
@@ -89,7 +93,6 @@ class AWS(CloudDeployment):
     instance_type: str
     home_dir: str
     repo: str
-    region_name: str
     runner_release: str = ""
     tags: list[dict[str, str]] = field(default_factory=list)
     gh_runner_tokens: list[str] = field(default_factory=list)
@@ -98,6 +101,7 @@ class AWS(CloudDeployment):
     security_group_id: str = ""
     iam_role: str = ""
     script: str = ""
+    region_name: Optional[str] = None
 
     def _build_aws_params(self, user_data_params: dict) -> dict:
         """Build the parameters for the AWS API call.
@@ -153,6 +157,10 @@ def create_instances(self) -> dict[str, str]:
             raise ValueError(
                 "No instance type provided, cannot create instances."
             )
+        if self.region_name is None and "AWS_DEFAULT_REGION" not in os.environ:
+            raise ValueError(
+                "No region name provided, cannot create instances."
+            )
         ec2 = boto3.client("ec2", region_name=self.region_name)
         id_dict = {}
         for token in self.gh_runner_tokens:
@@ -180,6 +188,10 @@ def create_instances(self) -> dict[str, str]:
         return id_dict
 
     def remove_instances(self, ids: list[str]):
+        if self.region_name is None and "AWS_DEFAULT_REGION" not in os.environ:
+            raise ValueError(
+                "No region name provided, cannot create instances."
+            )
         ec2 = boto3.client("ec2", self.region_name)
         params = {
             "InstanceIds": ids,
diff --git a/tests/test_aws.py b/tests/test_aws.py
index cd8f017..bd867ee 100644
--- a/tests/test_aws.py
+++ b/tests/test_aws.py
@@ -142,6 +142,15 @@ def test_create_instances_missing_instance_type(aws):
         aws.create_instances()
 
 
+def test_create_instances_missing_region(aws):
+    aws.region_name = None
+    os.environ.pop("AWS_DEFAULT_REGION")
+    with pytest.raises(
+        ValueError, match="No region name provided, cannot create instances."
+    ):
+        aws.create_instances()
+
+
 def test_instance_running(aws):
     ids = aws.create_instances()
     assert len(ids) == 1
@@ -202,6 +211,18 @@ def test_remove_instances(aws):
     assert not aws.instance_running(ids[0])
 
 
+def test_remove_instances_missing_region(aws):
+    ids = aws.create_instances()
+    assert len(ids) == 1
+    ids = list(ids)
+    aws.region_name = None
+    os.environ.pop("AWS_DEFAULT_REGION")
+    with pytest.raises(
+        ValueError, match="No region name provided, cannot create instances."
+    ):
+        aws.remove_instances(ids)
+
+
 def test_wait_until_removed(aws):
     ids = aws.create_instances()
     assert len(ids) == 1