Tennis was a racquet sport played on Earth. The sport had three variations, none of which Romana was familiar with: real, lawn and table tennis. K9 erased all his knowledge of tennis from his memory banks when he followed Romana's instructions to "forget it" literally. (TV: The Stones of Blood)
Later in the Doctor's life, Jack Harkness tried on a tennis outfit complete with racquet for a TV show but did not seem to like it, claiming it was "too safe". (TV: Bad Wolf) Still later, the Tenth Doctor used a tennis racquet to hit General Staal's probic vent. (TV: The Sontaran Stratagem)
Peri and Erimem played tennis while posing as the Princes in the Tower. (AUDIO: The Kingmaker)
The pleasure planet A-Lux had sub-aqua tennis courts. (COMIC: A Cold Day in Hell!)
Ernest Tiermann's Dreamhome had tennis courts. (PROSE: Sick Building)
Sebastian Vaughan enjoyed playing tennis when he was younger. (AUDIO: The Vigil)