Actix is a typed actor framework for Rust, built on top of Tokio. It provides a runtime for concurrent message-passing between actors, supporting both asynchronous and synchronous execution contexts. The framework defines core traits (Actor, Handler, Message) and provides an address-based communication model (Addr, Recipient) with bounded mailboxes and backpressure. It includes built-in supervision for fault tolerance, a system registry for service discovery, and a message broker for publish-subscribe patterns. The library is designed for building highly concurrent networked applications, and is the foundation for the actix-web HTTP framework. Architecturally, the system is centered around the System and Arbiter runtime components. Actors are spawned into contexts (Context for async, SyncContext for CPU-bound work) and communicate via typed messages. The address channel implementation uses a lock-free MPSC queue with capacity control. The framework provides a rich set of future and stream combinators (ActorFuture, ActorStream) that allow chaining asynchronous operations with access to actor state. External dependencies include tokio, futures, actix-rt, and crossbeam-channel. Key entry points include Actor::start(), Context::run(), System::new(), and the #[actix::main] macro. The library is extensively tested with unit tests, integration tests, and benchmarks. It is actively maintained with a clear changelog and migration guide.