The journey capped the first voyage by humans to the vicinity of the moon in more than 50 years.
NASA's gumdrop-shaped Orion capsule, dubbed Integrity, parachuted gently into the sea off the Southern California coast shortly after 5pm on Friday US Pacific time, concluding a mission that took the astronauts deeper into space than anyone had flown before.
The Artemis II flight, travelling a total of 1,117,51km across two Earth orbits and a climactic lunar flyby some 405,555km away, was the debut crewed test flight in a series of Artemis missions that aim to start landing astronauts on the lunar surface starting in 2028.
Recovery teams were standing by to secure the floating capsule and retrieve the crew - US astronauts Reid Wiseman, 50, Victor Glover, 49, and Christina Koch, 47, along with Canadian astronaut Jeremy Hansen, 50.
The crew's homecoming cleared a critical final hurdle for the Lockheed Martin-built Orion spacecraft, proving it would withstand the extreme forces of re-entry from a lunar-return trajectory.
It followed a white-knuckle, 13-minute fiery plunge through Earth's atmosphere, generating frictional heat that sent temperatures on the capsule's exterior soaring to some 2760C.
At the peak of re-entry stress, as expected, intense heat and air compression formed a red-hot sheath of ionised gas, or plasma, that engulfed the capsule, cutting off radio communications with the crew for several minutes.
The tension broke as contact was re-established and two sets of parachutes were seen billowing from the nose of the free-falling capsule, slowing its descent to about 25km/h before Orion gently hit the water.
It was expected to take NASA and US Navy teams about an hour to secure the floating capsule and assist the four astronauts out of the vehicle and fly them to a nearby recovery ship to undergo an initial medical check-up.
The quartet blasted off from Cape Canaveral, Florida, on April 1, lofted into an initial Earth orbit by NASA's giant Space Launch System rocket before sailing on for a rare journey around the far side of the moon.
In so doing, they became the first astronauts to fly in the vicinity of Earth's only natural satellite since the Apollo program of the 1960s and 70s. Glover, Koch and Hansen also made history as the first Black astronaut, the first woman and first non-US citizen, respectively, to take part in a lunar mission.
At the flight's peak, the Artemis astronauts reached a point 406,771km from Earth, exceeding the previous record of 399,117km set in 1970 by the crew of Apollo 13.
The voyage, following the uncrewed Artemis I test flight around the moon by the Orion spacecraft in 2022, marked a critical dress rehearsal for a planned attempt later this decade to land astronauts on the lunar surface for the first time since Apollo 17 in late 1972.
The ultimate goal of the Artemis program is to establish a long-term presence on the moon as a stepping stone to eventual human exploration of Mars.
For many in a global audience captivated by the latest moon shot, it reaffirmed the achievements of science and technology at a time when big tech has become widely distrusted, even feared. Opinion polling showed broad public support for the aims of the mission.
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