mediaLib (from "multimedia library") is a portable low level library for accelerating multimedia applications, with interfaces in C. It was developed by Sun Microsystems and open-sourced under the CDDL license as part of the OpenSolaris project.

It is implemented in ANSI C, but can take advantage of SIMD multimedia instructions on various processors to gain a significant performance boost.

Since mediaLib is written in C and SIMD multimedia compiler intrinsics, it should be usable on any system that has an ANSI C compiler that supports SIMD multimedia intrinsics.

Systems without SIMD intrinsics support can also use it as pure ANSI C, forgoing any extra acceleration provided by SIMD multimedia instructions.

It is also included as part of Solaris 10. mediaLib 2.5 contains about 4000 files and 2.4 million lines of code, and contains more than 3000 functions for different areas: Open source applications that use mediaLib include Java, JDS for Solaris, mplayer, and ogle.