Marcin Kowalczyk is a Polish speedcuber specializing in blindfolded cubing.
Marcin set the multi-blind world record of 41/41 in September 2013, at SLS Świerklany 2013. He set multiple other MBLD records before this.
He attempted to get a 46/46 Multi-BLD WR three times at the World Championship 2017, but was unsuccessful with a 31/46 60:00.00, 40/46 59:27.00, and 30/46 59:39.00. He took second place at this World Championship.
His record had been the third longest-standing world record in the WCA at 1,589 days, only after Minh Thai's 7,749-day Rubik's cube world record, and Feliks Zemdegs' 1,617-day one-handed world record, before it was broken by Mark Boyanowski on 24 March 2018 at Keep Portland Quiet 2018.