Gnash is a media player for playing SWF files. Gnash is available both as a standalone player for desktop computers and embedded devices, as well as a plugin for the browsers still supporting NPAPI. It is part of the GNU Project and is a free and open-source alternative to Adobe Flash Player. It was developed from the gameswf project.

Gnash was first announced in late 2005 by software developer John Gilmore. As of 2011, the project's maintainer is Rob Savoye. The main developer's web site for Gnash is located on the Free Software Foundation's GNU Savannah project support server.

Gnash supports most SWF v7 features and some SWF v8 and v9, however SWF v10 is not supported.