RIO DE JANEIRO - American Lilly King is the new 100m breaststroke queen, winning her first Olympics gold medal in a Games-record 1min 4.93sec on Monday.

Russia's Yulia Efimova, who won her appeal against a doping ban on the eve of the Rio Olympics, finished in 1:05.50 to win silver. American Katie Meili took bronze (1:05.69).

World record holder and defending champion Ruta Meilutyte was seventh (1:07.32).

"Tonight has been so crazy. My life is changing right now," said King. "I'm a gold medallist and it's what I've always wanted to be and it's an incredible feeling.

"I'm probably going to start crying. I'm usually not a crier but this is a special moment so we'll see if it gets to me or not."

King showed who the No. 1 is after Efimova had wagged her finger following her victory in the first semi-final. King went on to post a quicker time to win the second semi-final, then called out the 24-year-old.

"You wave your finger 'No. 1' and you've been caught drug cheating… I'm not a fan", the 19-year-old told American broadcaster NBC.

Efimova was jeered during the final at the Olympic Aquatics Stadium - just as she was during the heats and semi-finals on Sunday.

The world champion was one of seven swimmers initially banned from the Games after the International Olympic Committee ruled that no Russian athletes who had received past doping bans would be allowed to compete.

Efimova was banned between October 2013 and February 2015 after testing positive for traces of the anabolic steroid DHEA.

Having served time, however, she argued that she should not be punished again, and she was cleared to compete in Rio by the Court of Arbitration for Sport.

"I'm just happy to be here," said Efimova. "A week ago I didn't even know if I'd race, because I'm Russian."