LiteStep is a Windows Shell replacement for Windows 9x and up, licensed under the terms of the GNU General Public License (GPL).

LiteStep replaces the Windows Shell which provides access to the graphical user interface on Windows-based computers. Depending on the theme used, it can replace or remove shell elements, such as the start menu and taskbar. It can also be used to create informational-type displays. Aside from the core executable, LiteStep is made up of modules, some of which are included with the initial installation. Other modules, which a theme may require to function properly, are automatically downloaded. The modules and core provide users with the ability to create anything from minimal environments, to elaborate and heavily scripted desktops. Customizations are provided in the form of themes, which may be created or modified with a text editor. A theme for LiteStep is a collection of configurations, scripts, and/or images which are distributed in a file with the zip or lsz extension. The lsz file extension is a renamed zip file, which is associated with the LiteStep Theme Installer.