T'Lani Prime was the inhabited prime planet of the T'Lani system.
In 2370, a T'Lani cruiser was located in orbit of the third planet, and Dr. Bashir and O'Brien were sent there to help the T'Lani and Kelleruns rid themselves of Harvesters, a biological weapon. After completing their task, there was to be a celebration held on T'Lani Prime, thus delaying their expected departure by a day.
Not long after, Ambassador E'Tyshra told Benjamin Sisko that there would be a memorial service held for Bashir and O'Brien on the planet, after their supposed deaths. (DS9: "Armageddon Game")
According to the script, the pronunciation for T'Lani was " tuh-LA-nee".