Spacemacs is a configuration framework for GNU Emacs. It can take advantage of all of GNU Emacs' features, including both graphical and command-line user interfaces, and being executable under X Window System and within a Unix shell terminal. It is free and open-source software (FOSS) released under the GPL-3.0-or-later license.

Spacemacs consists mainly of configuration files, pre-defined internal commands, and configurations for various plug-ins (called 'packages'). It features a novel mnemonic key binding design (e.g., commands for file manipulation often start with "f",) which attempts to improve ergonomics (and avoid emacs pinky), a system for adding or excluding pre-configured features called 'layers', and includes verbose software documentation. It has three user-selectable input modes: Emacs mode, Vim mode (based on the evil Emacs package for Vim emulation), and Hybrid mode.

As of 2021[update], its repository on GitHub has been starred over 21,100 times and has over 11,300 commits.