Neil Armstrong, the first man to walk on the moon, has died at the age of 82.
Armstrong died following complications resulting from cardiovascular procedures, a statement from his family said on Saturday.
Praising Armstrong as a "reluctant American hero", his family said they were heartbroken and noted that the space pioneer had "served his nation proudly, as a navy fighter pilot, test pilot and astronaut".
"While we mourn the loss of a very good man, we also celebrate his remarkable life and hope that it serves as an example to young people around the world to work hard to make their dreams come true, to be willing to explore and push the limits, and to selflessly serve a cause greater than themselves," they said in the statement.
As commander of the Apollo 11 mission, Armstrong landed on the moon on July 20, 1969.
As he stepped on the moon's dusty surface, Armstrong memorably declared: "That's one small step for man, one giant leap for mankind."
In a statement issued by the White House, President Barack Obama said Armstrong and the rest of the crew of Apollo 11 carried with them the aspirations of an entire nation when they set out for the moon in 1969.
The president says that when Armstrong set foot on the moon, he delivered what he called "a moment of human achievement that will never be forgotten".
NASA administrator Charles Bolden said "as long as there are history books, Neil Armstrong will be included in them".
Bolden issued a statement on Saturday on the famed astronaut's death, saying that Armstrong will be "remembered for taking humankind's first small step on a world beyond our own".
|Armstrong became a professor at the University of Cincinnati [NASA]
He said Armstrong was "one of America's greatest explorers" who readily accepted US President John F Kennedy's challenge to send an American to the moon.
An estimated 600 million people - one-fifth of the world's population - watched and listened to the landing, the largest audience for any single event in history.
Fellow astronaut Buzz Aldrin, who spent nearly three hours walking on the lunar surface with Armstrong, said he was "very saddened to learn of the passing".
"I know I am joined by millions of others in mourning the passing of a true American hero and the best pilot I ever knew," he said in a statement.
Armstrong underwent heart bypass surgery earlier this month to relieve blocked coronary arteries, according to the family's statement. It did not say where or when he died.
The Apollo 11 moon mission turned out to be Armstrong's last space flight.
The following year he was appointed to a desk job, being named NASA's deputy associate administrator for aeronautics in the office of advanced research and technology.
He left NASA a year later to become a professor of engineering at the University of Cincinnati in the US state of Ohio.
The former astronaut lived in the Cincinnati area with his wife, Carol.
"Neil was our loving husband, father, grandfather, brother and friend," the family said in its statement.