RTEMS
| Developer | OAR Corporation | 
|---|---|
| Written in | C | 
| OS family | Real-time operating system | 
| Working state | Current | 
| Source model | Open source | 
| Initial release | 1993 | 
| Latest release | 6.1 / January 22, 2025 | 
| Repository | gitlab | 
| Marketing target | Embedded systems | 
| Available in | English | 
| Platforms | ARM, Blackfin, ColdFire, TI C3x/C4x, H8/300, x86, 68k, LatticeMico32, Microblaze, MIPS Nios II, OpenRISC, PowerPC, SuperH, SPARC (ERC32, LEON), SPARC64 | 
| Kernel type | Real-time | 
| Default user interface | Command-line | 
| License | BSD 2 Paragraph | 
| Official website | www | 
Real-Time Executive for Multiprocessor Systems (RTEMS), formerly Real-Time Executive for Missile Systems, and then Real-Time Executive for Military Systems, is a real-time operating system (RTOS) designed for embedded systems. It is free and open-source software.
Development began in the late 1980s with early versions available via File Transfer Protocol (ftp) as early as 1993. OAR Corporation managed the RTEMS project in cooperation with a steering committee until the early 2000's when project management evolved into a subset of the core developers managing the project. In 2014, hosting was moved from OAR Corporation to the Oregon State University Open Source Lab hosting.