The number 21 on MLB uniforms is to honor Roberto Clemente, a legendary Puerto Rican baseball player who wore No. 21 for the Pittsburgh Pirates throughout his career. MLB commemorates Clemente's legacy with Roberto Clemente Day on September 15 each year, during which players, managers, and coaches wear a patch with the number 21. Additionally, players of Puerto Rican heritage and nominees or recipients of the Roberto Clemente Award have the option to wear No. 21 to celebrate his humanitarian and baseball achievements. The Pittsburgh Pirates also uniquely wear the number 21 across their roster on this day as an extra mark of respect. Clemente was a Hall of Famer, humanitarian, and a trailblazer as the first Latin American player elected to the Baseball Hall of Fame.

Significance of Number 21

• Worn by Roberto Clemente for his entire Major League career.
• Represents his impact both as a player and humanitarian.
• Clemente was a 15-time All-Star, 12-time Gold Glove winner, a member of the 3,000-hit club, and died delivering earthquake relief aid.
• MLB honors his legacy annually with the No. 21 patch and events on Roberto Clemente Day.

Who Wears No. 21

• All MLB players, managers, and coaches wear a 21 patch on Roberto Clemente Day.
• Players of Puerto Rican descent may wear No. 21 on their jerseys.
• Roberto Clemente Award nominees and recipients may also wear No. 21.
• The Pittsburgh Pirates wear No. 21 across their roster on this day.

This tradition started in 2020 and has continued as a sign of respect and inspiration in Major League Baseball.