Armstrong died following complications resulting from cardiovascular procedures, his family said in a statement. It didn't say where he died; he had lived in suburban Cincinnati.
Armstrong commanded the Apollo 11 spacecraft that landed on the moon July 20, 1969, capping the most daring of the 20th century's scientific expeditions. His first words after setting foot on the surface are etched in history books and the memories of those who heard them in a live broadcast.
"That's one small step for (a) man, one giant leap for mankind," Armstrong said.
In those first few moments on the moon, during the climax of a heated space race with the then-Soviet Union, Armstrong stopped in what he called "a tender moment" and left a patch to commemorate NASA astronauts and Soviet cosmonauts who had died in action.
Armstrong and Buzz Aldrin spent nearly three hours walking on the lunar surface, collecting samples, conducting experiments and taking photographs.
The moonwalk marked America's victory in the Cold War space race that began Oct. 4, 1957, with the launch of the Soviet Union's Sputnik 1, a 184-pound satellite that sent shock waves around the world.