The 2021 Phillips 66 Big 12 men's basketball tournament was a postseason men's basketball tournament for the Big 12 Conference. It was played from March 10 to 13, in Kansas City, Missouri at the T-Mobile Center. The winner received the conference's automatic bid to the 2021 NCAA tournament. Texas defeated Oklahoma State in the championship to earn their first Big 12 Tournament Championship and third Conference tournament Championship overall. Texas became the first school that was not a member of the Big Eight Conference to win the tournament.