US astronaut John Young, who walked on the moon in 1972 and was the only person to fly with three NASA space programs, has died aged 87.
Mr Young, who went to space six times, died on Friday night at his home in Houston following complications from pneumonia, National Aeronautics and Space Administration spokesman Allard Beutel said in an email.
The former US Navy test pilot was the ninth person to set foot on the moon, an experience shared by three others after Mr Young.
He eventually became one of the most accomplished astronauts in the history of the US space program.
He flew into space twice during NASA's Gemini program in the mid-1960s, twice on the Apollo lunar missions and twice on space shuttles in the 1980s. He was the only person to fly on all three types of programs.
"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," NASA Administrator Robert Lightfoot said in a statement.
Mr Young, described in a NASA tweet as "our most experienced astronaut", retired in 2004 after 42 years with the US space agency.
The Apollo 16 mission in April 1972, his fourth space flight, took Mr Young to the lunar surface.
As mission commander, he and crewmate Charles Duke explored the moon's Descartes Highlands region, gathering 90kg of rock and soil samples and driving more than 26 km in the lunar rover to sites such as Spook Crater.
Mr Young's first time in space came in 1965 with the Gemini 3 mission that took him and astronaut Gus Grissom into Earth orbit in the first two-person US space jaunt.
It was on this mission that Mr Young smuggled aboard a corned beef sandwich, which did not make NASA brass happy but certainly pleased Mr Grissom, the recipient of the snack.
NASA rebuked Mr Young for the antics, which generated criticism from lawmakers and the media, but his career did not suffer.
His May 1969 Apollo 10 mission served as a "dress rehearsal" for the historic Apollo 11 mission two months later in which Neil Armstrong became the first person to walk on the moon.
Mr Young's fifth space mission was as commander of the inaugural flight of NASA's first space shuttle, Columbia, in 1981. He became the first person to fly six space missions in 1983, when he commanded Columbia on the first Spacelab trek, with the crew performing more than 70 scientific experiments.
"John was more than a good friend," former President George HW Bush said in a statement. "He was a fearless patriot whose courage and commitment to duty helped our nation push back the horizon of discovery at a critical time."
Mr Young was born on September 24, 1930, in San Francisco and grew up in Orlando, Florida. After receiving a degree in aeronautical engineering from the Georgia Institute of Technology in 1952, he entered the Navy and graduated from its test pilot school. NASA picked him in 1962 for its astronaut program.