Lya is a Federation planet that is located near Cardassian space.
Lya Station Alpha orbited Lya. In 2368, the USS Enterprise visited Lya to dock at the starbase. (TNG episode: "Ensign Ro")
In 2376, Shakaar Edon visited Lya as part of a diplomatic tour of the Federation. At the time, Shakaar had been infected by a parasite that had attacked him on Minos Korva. (DS9 novel: Unity)