Serena Williams: Six Memorable Grand Slam Finals

Serena Williams announced on Tuesday the countdown to her retirement had begun from tennis after a career which brought her 23 Grand Slam singles titles. AFP Sport looks at six of her most memorable finals at the majors:

Just 17 years old, the first of her Slam titles came at Flushing Meadows courtesy of a 6-3, 7-6 (7/4) win over Switzerland's Martina Hingis. Williams had defeated the likes of Conchita Martinez, Monica Seles and 1998 champion Lindsay Davenport on the way. She was also the first black woman to win a major since Althea Gibson in 1958.

"It's really amazing for me just to even have an opportunity to be compared as great as Althea Gibson. She was a great player. It's pretty exciting for me," she said.

Serena had to wait the best part of three years to win a second Slam with a 7-5, 6-3 victory over sister Venus in the final at Roland Garros. Venus had won the sisters' only other previous meeting in a major final in New York in 2001.

"I am so happy to have won my second Grand Slam in three years, but obviously I am also a little bit sad for my sister," said Serena who went on to win the French Open again in 2013 and 2015.

The 2002 title match in Paris was the first of four consecutive Slam finals between the sisters with Serena winning all four.

Williams wins her first Australian Open and completes the 'Serena Slam' after an epic 7-6 (7/4), 3-6, 6-4 win against Venus.

The world number one became only the fifth woman in history to hold all four Slams at the same time after Maureen Connolly, Margaret Court, Martina Navratilova and Steffi Graf.

"I can't believe that I can be compared to these women, to be in their category is really amazing," she said.

"I am making history right now, it doesn't happen every day."