Wine is a piece of software which lets Unix-like computer operating systems on the x86 and x86-64 architectures to execute programs written for Microsoft Windows. Wine runs Windows programs without using emulation. Wine also provides a software library known as Winelib which developers can compile Windows applications against to help port them to Unix-like systems. Some Wine code is used in ReactOS, a free operating system that is Windows-compatible and is not based on Unix.

The Wine developers released version 1.0 of Wine, after 15 years of development, on June 17 2008. Wine is free software, released under terms of the GNU Lesser General Public License (LGPL).