Cilk is a language for multithreaded parallel programming based on ANSI C. Cilk is designed for general-purpose parallel programming, but it is especially effective for exploiting dynamic, highly asynchronous parallelism, which can be difficult to write in data-parallel or message-passing style.

Cilk was developed by the MIT CSAIL Supercomputing Technologies Group under the leadership of prof. Charles Leiserson.

Cilk is released under the GNU General Public License.