Two NFL stars put their manliness to the test in Finland -- ICE SWIMMING IN 34 DEGREE WATER ... and TMZ Sports has the video.
Steelers running back DeAngelo Williams and Browns tight end Gary Barnidge made the leap at Loyly Helsinki ... where the outside temperature was a cozy 20 DEGREES!
The guys are in Finland as part of the American Football Without Barriers program which helps spread the game to other countries.
Also there ... Atlanta Falcons Pro Bowl center Alex Mack -- who did TOPLESS SNOW ANGELS!!