Yukihiro Matsumoto (まつもとゆきひろ 松本行弘 Matsumoto Yukihiro^?, a.k.a. 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).

As of 2011, Matsumoto is the Chief Architect of Ruby at Heroku, an online cloud platform-as-a-service in San Francisco. He is the fellow of Rakuten Institute of Technology, a research and development organization in Rakuten Inc.

Matsumoto's name can be written using kanji: 松本行弘, but is normally written using hiragana: まつもとゆきひろ.

Born in Osaka Prefecture, he was raised in Tottori Prefecture from the age of four. According to an interview conducted by Japan Inc., he was a self-taught programmer until the end of high school.^[1] He graduated with an information science degree from University of Tsukuba, where he was a member of Ikuo Nakata's research lab on programming languages and compilers. Matsumoto is married and has four children. He is a member of The Church of Jesus Christ of Latter-day Saints, did standard service as a missionary and is now a counselor in his church ward.

Matz released the first version of the Ruby programming language on December 21, 1995^[3][4] and he is still leading the development effort on the reference implementation often called MRI for Matz Ruby Implementation.