Sibelius Software is a London-based software business and a part of Avid Technology that develops and sells music notation and music education software.

The company was named after the Finnish composer Jean Sibelius, and was founded in April 1993 by twins Ben and Jonathan Finn to sell the Sibelius notation program. In addition to its head office in London, Sibelius Software opened offices in the US, Japan and Australia, with distributors and dealers in many other countries worldwide.

In August 2006 the company was acquired by Avid, to become part of its Digidesign division, which also manufactures the leading digital audio workstation Pro Tools.

The company has won numerous awards, including the Queen's Award for Innovation in 2005.

The company's best-known product, Sibelius, was first released (under the name Sibelius 7) for Acorn computers in 1993. Sibelius Software also sold Acorn computers, printers, MIDI equipment, word processing & graphics software, etc. because at that time many of its customers did not already have a computer; but the company stopped selling these products (and developing Acorn software) when it released Sibelius for Windows in September 1998. This was followed by a Mac version in March 1999. From the Windows release, the unusual suffix '7' was dropped from the Sibelius product name, and the version number restarted at 1.0.