The role of a compiler in programming is to translate source code written in a high-level programming language into machine code that a computer's processor can execute. This translation process involves various stages, including lexical analysis, syntax analysis, semantic analysis, optimization, and code generation. Compilers ensure that the program adheres to the syntax and semantics of the language and optimize the code for performance. By converting human-readable code into efficient machine code, compilers bridge the gap between programming languages and computer hardware.