A planet rich in dilithium whose proposed admission to the Federation is the subject of the Babel conference, and which Enterprise shows as a populous, divided world a century earlier.
Coridan is the home of the Coridanites. In the original series episode Journey to Babel, delegates travel aboard the Enterprise to decide whether the underpopulated but mineral-rich planet should join the Federation, a move that would protect it from illegal mining. Sarek argues in favour of admission.
Enterprise visits the planet in the 2150s. Shadows of P'Jem shows a Vulcan-backed government fighting rebels supported by the Andorians, and Coridan sends representatives to the talks seen in Demons and Terra Prime.
Later productions treat Coridan as a Federation member, and Coridanites are mentioned from time to time in the series set in the 24th century.