Twelve men have walked on the Moon, all US astronauts of the Apollo program.
They were :
Apollo 11 (July 20, 1969)- Neil Armstrong and Edwin "Buzz" Aldrin (the first men to walk on the Moon)
Apollo 12 - Charles Conrad, Jr. and Alan Bean
Apollo 14 - Alan Shepard Jr. and Edgar Mitchell (Shepard was also the first US 'man in space' in 1961).
Apollo 15 - David Scott and James Irwin
Apollo 16 - John Young and Charles Duke, Jr.
Apollo 17 - Eugene Cernan and Dr. Harrison Schmitt
(Cernan was the last man to walk on the moon on December 14, 1972)
--see the related question below
12 People have stood on the moon, Neil Armstrong included.