Architecture where each request is completely independent with no memory of previous requests. Like a vending machine that doesn't remember who used it before - every transaction is fresh.
A stateless web API treats each request separately, so you can send the same request to any server in a cluster and get the same result, making it easy to scale.
Stateless is an application design principle, not a single cloud service. Many managed compute and API services across AWS, Azure, GCP, and OCI are commonly used to run stateless workloads (for example, load-balanced web apps, containers, and serverless functions).