Guillermo "Memo" Luna Romero (June 25, 1930 – November 9, 2021) was a Mexican professional baseball player, a left-handed pitcher whose career extended from 1949 through 1961 and who pitched one game of Major League Baseball for the 1954 St. Louis Cardinals. Luna was born in Mexico City. At the height of his career, he stood 6 feet (1.83 m) tall and weighed 168 pounds (76 kg). Luna was sent down to the Triple-A Rochester Red Wings after that one appearance, and never returned to the Majors. In 1988 he was selected to the Mexican Professional Baseball Hall of Fame.