Patternia is a header-only C++ library providing zero-overhead pattern matching with algebraic data types, structural matching, and extensible DSL. It leverages template metaprogramming to compile patterns into efficient switch-like code, eliminating runtime overhead for simple cases. The library includes a comprehensive test suite, benchmarks comparing against standard alternatives, and documentation. Its architecture emphasizes expression guards, combinators, and optimization passes, making it suitable for performance-critical applications requiring pattern matching.