The 70-year-old uncle of Hollywood star Matt Damon has become the oldest person to swim the English Channel.
Mr Brunstad is a champion swimmer who has won lots of medals
George Brunstad arrived on the French beach of Sangatte just after 0100 BST on Sunday, after 15 hours and 59 minutes in the water.
The retired US airline pilot set off from Dover on Saturday morning for the gruelling 21-mile swim.
He had originally planned to make the crossing on Wednesday, his 70th birthday, but bad weather delayed him.
'Praise the Lord'
Mr Brunstad, who lives in Connecticut, said he felt wonderful after the achievement.
"I am tired, but this is it, I've got the world record and I feel wonderful.
"When I arrived I just said 'Praise the Lord', stood on the beach and raised my arms in a V sign," he said.
He took a year to prepare for the challenge, training in the cold waters off the coast of Maine.
He took the record from 67-year-old Australian Bertram Batts, who made the crossing in 1987.
Mr Brunstad, who retired as an American Airlines pilot in 1994, is an experienced long-distance swimmer who has won more than 100 national championship medals in US Masters Swimming.
Mr Brunstad's record-breaking swim raised thousands of dollars for his charity Centre for Hope, set up to help children in Haiti following a trip with his wife to the village of Hinche.