BeOS was an operating system for personal computers which began development by Be Inc. in 1991. It was first written to run on BeBox hardware. BeOS was optimized for digital media work and was written to take advantage of modern hardware facilities such as symmetric multiprocessing by utilizing modular I/O bandwidth, pervasive multithreading, preemptive multitasking and a 64-bit journaling file system known as BFS. The BeOS GUI was developed on the principles of clarity and a clean, uncluttered design. It used Unicode as the default encoding in the GUI, yet support for input methods such as bidirectional input was never realized. The API was written in C++ for ease of programming. It has partial POSIX compatibility and access to a command-line interface through Bash, although internally it is not a Unix-derived operating system.

BeOS was positioned as a multimedia platform which could be used by a substantial population of desktop users and a competitor to Linux, Mac OS and Microsoft Windows. However, it was ultimately unable to achieve a significant market share and proved commercially unviable for Be Inc. The company was acquired by Palm Inc. and today BeOS is mainly used and developed by a small population of enthusiasts.