diff --git a/action.yml b/action.yml
index 31dcc00..88f1cfe 100644
--- a/action.yml
+++ b/action.yml
@@ -334,11 +334,51 @@ runs:
           echo "${env}-${cluster}"
         }
 
+        deactivate_stale_deployments () {
+          local environment="$1"
+
+          local deployments_response
+          deployments_response=$(curl -s \
+            -H "Accept: application/vnd.github+json" \
+            -H "Authorization: Bearer ${GITHUB_TOKEN_INPUT}" \
+            -H "X-GitHub-Api-Version: 2022-11-28" \
+            "https://api.github.com/repos/${GITHUB_REPOSITORY}/deployments?environment=${environment}&per_page=30")
+
+          local deployment_ids
+          deployment_ids=$(echo "$deployments_response" | jq -r '.[].id // empty')
+
+          for dep_id in $deployment_ids; do
+            local status_response
+            status_response=$(curl -s \
+              -H "Accept: application/vnd.github+json" \
+              -H "Authorization: Bearer ${GITHUB_TOKEN_INPUT}" \
+              -H "X-GitHub-Api-Version: 2022-11-28" \
+              "https://api.github.com/repos/${GITHUB_REPOSITORY}/deployments/${dep_id}/statuses?per_page=1")
+
+            local latest_state
+            latest_state=$(echo "$status_response" | jq -r '.[0].state // empty')
+
+            if [[ "$latest_state" == "in_progress" || "$latest_state" == "queued" || "$latest_state" == "pending" ]]; then
+              echo "Marking stale deployment ${dep_id} (${latest_state}) as inactive" >&2
+              curl -s \
+                -X POST \
+                -H "Accept: application/vnd.github+json" \
+                -H "Authorization: Bearer ${GITHUB_TOKEN_INPUT}" \
+                -H "X-GitHub-Api-Version: 2022-11-28" \
+                "https://api.github.com/repos/${GITHUB_REPOSITORY}/deployments/${dep_id}/statuses" \
+                -d '{"state": "inactive", "description": "Superseded by newer deployment"}' > /dev/null
+            fi
+          done
+        }
+
         create_deployment () {
           local environment="$1"
           local image="$2"
           local tag="$3"
 
+          # Deactivate any previous in-progress deployments for this environment
+          deactivate_stale_deployments "${environment}"
+
           RESPONSE=$(curl -s -w "\n%{http_code}" \
             -X POST \
             -H "Accept: application/vnd.github+json" \