Matias Koski (born 18 May 1994) is a Finnish swimmer. At the 2012 Summer Olympics, he competed in the Men's 400 metre freestyle, finishing in 22nd place in the heats. He also competed in the Men's 200 metre freestyle, winning his heat, but finishing in 31st in the heats and the Men's 1500 metre freestyle, finishing in 26th place in the heats.