Darius Olavi Koski (born January 3, 1971) is the US-American lead guitarist and songwriter of the punk rock band Swingin' Utters, the alternative punk rock bands Filthy Thievin' Bastards and the Re-volts. He also works as a plumber.

Koski has produced such acts as the Workin' Stiffs (Liquid Courage, 1999), Reducers SF (Backing the Long Shot, 1999), and The truents (Every Day of the Week, 1999).