Markku Juhani ”Mato” Valtonen (born 21 February 1955 in Loimaa) is a Finnish actor, musician and entrepreneur.

Valtonen has been a member of the Finnish band Sleepy Sleepers since 1975 and the Leningrad Cowboys since 1989.

[1] He was the CEO of WAPit telecommunications company from its inception in 1998[1] until it declared bankruptcy in 2001.

[2] As an actor, Valtonen is best known for starring in Aki Kaurismäki's films starting with 1985's Calamari Union.

Valtonen got the nickname at age 14 when he was at a cold summer cabin and crawled around on the floor wrapped in a sleeping bag, resembling a worm.