Monotone is a free distributed version control system. It provides a simple, single-file transactional version store, with fully disconnected operation and an efficient peer-to-peer synchronization protocol. It understands history-sensitive merging, lightweight branches, integrated code review and 3rd party testing. It uses cryptographic version naming and client-side RSA certificates. It has good internationalization support, has no external dependencies, runs on NetBSD, Linux, Solaris, OSX and Windows (among others), and is licensed under the GNU GPL.