Kaj Sigurd Ademar Arnö (born 29 June 1963 in Helsinki, Finland) is a Finland-Swedish IT-entrepreneur and columnist.

[2] He is the former Vice President of the MySQL Community at MySQL AB, Sun Microsystems and Oracle Corporation, founder of MariaDB Corporation Ab and the current CEO of the MariaDB Foundation.

[3] Arnö went to the Swedish co-educational school Nya svenska samskolan.

[5] In 2010, Arnö was co-founder together with Michael "Monty" Widenius and others of SkySQL, a company that sold support and consultancy for MySQL and MariaDB, which later became MariaDB Corporation Ab.

[3] Arnö has been a regular columnist in Swedish for Forum för ekonomi och teknik (2008-2021),[11] Svenska Yle's culture pages (2015-2021)[12][13] and Åbo Underrättelser since 2021.