Tyrellia was an inhabited planet, known for being only one of three such planets to lack a magnetic pole and one of only seven without any kind of atmosphere. Tyrellia was also the homeworld of the Tyrellians.

Starfleet officer Calvin Hutchinson was once stationed on Tyrellia during the mid-24th century. (TNG: "Starship Mine")

This planet was only mentioned in dialogue.
Data noted that there were five Tyrellians stationed aboard the USS Enterprise-D.