The father of actress Grace Kelly won three Olympic gold medals in which sport?

John Brendan Kelly Sr. (1889 – 1960), known as Jack Kelly, was one of the most accomplished American competitors in the history of the sport of rowing. He was the father of actress Grace Kelly, Princess of Monaco and of John B. Kelly Jr. who was also an accomplished rower. He was also a multimillionaire in the bricklaying and construction industry.

He was a gifted athlete and competed in football, basketball and rowing which he learned on the Schuylkill River. By 1916, Kelly was a national champion and the best sculler in the US. As part of the WWI call up, he joined the US Army as a private in October 1917 and rose to the rank of lieutenant when he was discharged in April 1919.

While in the army, he entered the armed forces boxing tournament as a heavyweight and ran up a 12–0 record before being waylaid by a broken ankle. Future world professional boxing champion Gene Tunney won the tournament. In later years, Kelly would kid Tunney: "Aren't you lucky I broke my ankle?

Kelly represented the US at the 1920 Summer Olympics in Antwerp, Belgium and won gold in the single scull event. Kelly and his cousin Paul Costello won gold in the double scull race only half an hour after his single skulls victory.

In 1924, Kelly and Costello repeated their success, winning the double-scull event at the Summer Olympics in Paris. This made Kelly the first rower to win three Olympic gold medals and one of the most famous and successful athletes of his generation.