Russia's Maria Sharapova reacts after defeating Slovakia's Daniela Hantuchova in her Stanford Classic tennis match in Stanford, California, July 27, 2011. [Photo/Agencies]

Tennis player Li Na of China laughs during a news conference at a promotional event in Beijing, July 14, 2011. [Photo/Agencies]

Maria Sharapova may not have won a grand slam title since 2008, but the Russian tennis player remains unchallenged as the world's highest paid woman in professional sports.

For the seventh straight year, Sharapova topped the annual list provided by Forbes magazine, despite failing to add to her three grand slam titles, although she did make the Wimbledon final in July.

Sharapova's earnings, mostly off-court endorsements, were estimated at $25 million, twice as much as her nearest rival, Denmark's Caroline Wozniacki, the current women's world number one.

American racing driver Danica Patrick was third with $12 million followed by tennis players Venus Williams, Belgium's Kim Clijsters and Serena Williams.

Seven of the top nine female earners were tennis players, including China's Li Na, who made $8 million last year but was expected to soar up the rankings and challenge Sharapova for the top spot after her breakthrough win at the French Open.

Top 10 women earners

1. Maria Sharapova $25 million (Russia, tennis)

2. Caroline Wozniacki $12.5 million (Denmark, tennis)

3. Danica Patrick $12 million (US, motor racing)

4. Venus Williams $11.5 million (US, tennis)

5. Kim Clijsters $11 million (Belgium, tennis)

6. Serena Williams $10.5 million (US, tennis)

7. Kim Yu-na $10 million (figure skating, South Korea)

8. Li Na $8 million (China, tennis)

9. Ana Ivanovic $6 million (Serbia, tennis)

10. Paula Creamer $5.5 million (US, golf)