Matz, born 14 April 1965) is a Japanese computer scientist and software programmer best known as the chief designer of the Ruby programming language and its reference implementation, Matz's Ruby Interpreter (MRI).
His demeanor has brought about a motto in the Ruby community: "Matz is nice and so we are nice," commonly abbreviated as MINASWAN.
As of 2011, Matsumoto is the Chief Architect of Ruby at Heroku, an online cloud platform-as-a-service in San Francisco.
He is a fellow of Rakuten Institute of Technology, a research and development organisation in Rakuten Inc.
He was appointed to the role of technical advisor for VASILY, Inc.