Alfonso Márquez (born April 12, 1972 in Zacatecas, Zac., Mexico) is an umpire in Major League Baseball who has worked in the National League in 1999 and throughout both major leagues since 2000. He has officiated in the 2006 World Series, the 2003 American League Championship Series, and four Division Series (2001, 2002, 2005, 2006), as well as the 2006 All-Star Game. The first Mexican-born umpire in major league history, he resides in Gilbert, Arizona. Márquez wears the uniform number 72.
While a minor league umpire, Márquez served as an instructor at the Brinkman/Froemming Umpire School.
For the 2009 season, Márquez is assigned to Randy Marsh's Crew P along with Mike Winters and Lance Barksdale.