Alfonso Márquez (born April 12, 1972) is a Mexican umpire in Major League Baseball (MLB) who worked in the National League in 1999 and has worked throughout both major leagues since 2000. He was promoted to crew chief for the 2020 season, becoming the first full time Latino-born crew chief. Márquez wears uniform number 72, a number he shared with friend and National Hockey League linesman Stéphane Provost.