Major League Baseball (MLB) players are wearing the number 21 today to honor Roberto Clemente. This is because MLB is celebrating Roberto Clemente Day on September 15, 2025, a day dedicated to recognizing the legacy of the Hall of Famer and humanitarian, who wore No. 21 throughout his career. All players, managers, coaches, and umpires wear a white "21" patch on their uniforms as part of the league-wide recognition. Additionally, players of Puerto Rican heritage, past Roberto Clemente Award recipients, and the current nominees can wear No. 21 on their uniforms during games today. The Pittsburgh Pirates, Clemente's team for his entire career, also wear No. 21 across their rosters in tribute. This day also marks the start of National Hispanic Heritage Month and celebrates Clemente's achievements and humanitarian efforts.