GW-BASIC is a dialect of the BASIC programming language developed by Microsoft from IBM BASICA. Functionally identical to BASICA, its BASIC interpreter is a fully self-contained executable and does not need the Cassette BASIC ROM found in the original IBM PC. It was bundled with MS-DOS operating systems on IBM PC compatibles by Microsoft.

The language is suitable for simple games, business programs and the like. Since it was included with most versions of MS-DOS, it was also a low-cost way for many aspiring programmers to learn the fundamentals of computer programming. Microsoft also sold a BASIC compiler, BASCOM, compatible with GW-BASIC, for programs needing more speed.

According to Mark Jones Lorenzo, given the scope of the language, "GW-BASIC is arguably the ne plus ultra of Microsoft's family of line-numbered BASICs stretching back to Altair BASIC – and perhaps even of line-numbered BASIC in general."

With the release of MS-DOS 5.0, GW-BASIC's place was taken by QBasic, a slightly abridged version of the interpreter part of the separately available QuickBASIC interpreter and compiler package.

On May 21, 2020, Microsoft released the 8088 assembler source code for GW-BASIC 1.0 on GitHub under the MIT License.