The couple are both sponsored by sportswear giant ADIDAS and met at a product launch.
The Swiss, who retired three years ago because of chronic injuries, enjoys romantic liaisons with Campbell, 30, as often as she can, but their busy schedules mean they spend most of their time apart.
Hingis says, "I like Sol a lot and we see each other whenever possible but he has many matches and I have my appointments. It is not easy."
But the 24-year-old isn't sure if they are in love yet, explaining, "That's too strong a word."
Campbell enjoyed a brief relationship with British singer Dido last year (04).15/02/2005 13:48
Rihanna is one mean criminal in the gangster thriller that is her hugely anticipated (and highly explicit) video for the single 'B***h Better Have My...
There's a lot to look forward for Wireless' 10th anniversary event.
The pop star burned part of the flag after she spotted it walking round the Glastonbury camp site.
Oscar unveils the title track to his newly released debut EP 'Beautiful Words', out now on Wichita Recordings.
Soul legend Lionel Richie could be headed back to the top of the charts, with the news...
The Hollywood duo - who have children Violet, nine, Seraphina, six, and Samuel...