Olympic champion and world number one Serena Williams was bundled out of the Rio 2016 tennis tournament in the third round of the singles competition after a shocking 6-4 6-3 defeat to Ukraine's Elina Svitolina.
Tuesday's defeat by the 20th-ranked Svitolina ends Williams' Olympic tournament, having also suffered a surprise loss in the doubles tournament with her older sister Venus on Sunday.
The 34-year-old Williams, who is not entered in the mixed doubles competition, cut short her media commitments after the loss, speaking only to the official broadcasters before she returned to the changing rooms.
"It was a great opportunity. It didn't work out the way I wanted it to, but at least I was able to make it to Rio. That was one of my goals," said Serena.
Svitolina, who will face Czech Republic's Petra Kvitova in the quarter-finals, was over the moon with her first victory in five meetings over the 22-time grand slam singles winner.
"It's an unreal feeling for me. This is just a perfect moment," said Svitolina.
Williams grew increasingly frustrated during the match as she struggled to find her range, making 37 unforced errors compared with 17 by the 21-year-old Ukrainian.
Williams' defeat came hours after third-seed and French Open champion Garbine Muguruza was knocked out by Puerto Rico's Monica Puig.
Germany's world number two Angelique Kerber, who beat Williams in the final of the Australian Open in January but lost the Wimbledon final to the American, is now the favourite for gold.
Williams had won three doubles Olympic titles with Venus. Their first round loss to Czech duo Barbora Strycova and Lucie Safarova was their first-ever Olympic loss in the doubles competition.
They won the title in Sydney, did not pair up for Athens due to an injury Serena had at the time, but reclaimed the title in Beijing and then defended it in London.
The pair has also won 14 women's doubles grand slam titles.