The Eighth Galaxies were a group of galaxies. A Micro Servo Robot spoke an ad to Jo Grant offering a credit-chip that would be accepted anywhere in the Eight Galaxies. (AUDIO: Pop-Up)
Circa 2996, Ketch claimed to entertain people across the Eight Galaxies, but then thought it could've been nine, saying it was "definitely more than three". (AUDIO: Terror of the Sontarans)