John Young, one of only 12 people to have walked on the Moon, has died at the age of 87, NASA has announced.
The US agency said on Saturday that the former astronaut's death was due to complications following pneumonia.
Young is the only astronaut who took part in the Gemini, Apollo and space shuttle programmes.
"Today, NASA and the world have lost a pioneer," Robert Lightfoot, NASA administrator, said in a statement.
"Astronaut John Young's storied career spanned three generations of spaceflight; we will stand on his shoulders as we look toward the next human frontier."
Born in San Francisco in 1930, Young joined the US Navy in 1952.
Ten years later, he was selected to join NASA and in 1965 he made he made his first trip to space with Gus Grissom on Gemini 3.
In 1969, Young was the commander of the Apollo 10 flight to the Moon, a preparation flight for the eventual Apollo 11 Moon landing several months later.
In 1972, Young landed on the Moon himself during the Apollo 16 mission. He spent three lunar nights on the surface and drove more than 25km in a lunar rover.
"The Moon is a very nice place," he had said. "When we landed, we were 20 minutes behind. Because time on the Moon was so precious, what I remember most is trying to catch up."
In 1981, meanwhile, he commanded the first space shuttle flight.
Twelve people walked on the Moon between 1969 and 1972. Five of them are still alive, including Buzz Aldrin, who was part of the first landing.