Jari "Jartsi" Kainulainen (born 29 April 1970) is a Finnish bass guitarist.

In 2007, he joined the Swedish progressive power metal band Evergrey.

In 2010, Jari Kainulainen created the power metal supergroup Symfonia along with Andre Matos, Timo Tolkki, Mikko Härkin and Uli Kusch.

Kainulainen plays Ibanez six-string basses and uses Ampeg amplifiers.

He is influenced by Geezer Butler, Billy Sheehan, Cliff Burton, and Steve Harris.