Legendary astronaut John Young, who walked on the moon and later commanded the first space shuttle flight, has died aged 87.
Space agency Nasa said he died on Friday night following complications from pneumonia.
It said he "was one of that group of early space pioneers whose bravery and commitment sparked our nation’s first great achievements in space".
Nasa said Mr Young was the only agency astronaut to go into space as part of the Gemini, Apollo and space shuttle programmes.
He was also the first to fly into space six times and the ninth man to walk on the moon.
He died at home in Houston.
Young was in Nasa’s second astronaut class, chosen in 1962, along with the likes of Neil Armstrong, Pete Conrad and James Lovell.
"Today, Nasa and the world have lost a pioneer. Astronaut John Young’s storied career spanned three generations of spaceflight," administrator Robert Lightfoot said.
Counting his takeoff from the moon in 1972 as commander of Apollo 16, Mr Young’s blastoff tally stood at seven, for decades a world record.
He flew twice during the two-man Gemini missions of the mid-1960s, twice to the moon during Nasa’s Apollo programme, and twice more aboard the new space shuttle Columbia in the early 1980s.
Mr Young spent his last 17 years at Nasa’s Johnson Space Centre in Houston in management, focusing on safety issues. He retired at the end of 2004.
Former president George HW Bush said he and wife Barbara "join our fellow Americans and many friends in the space community in mourning the loss".
He went on: "John was more than a good friend; he was a fearless patriot whose courage and commitment to duty helped our nation push back the horizon of discovery at a critical time.
"To us, he represented the best in the American spirit - always looking forward, always reaching higher."
He added: "John leaves a tremendous legacy of accomplishment, in addition to his wonderful family.
"May his memory serve to inspire future generations of explorers to dare greatly, act boldly and serve selflessly."