Trégastel (French pronunciation: [tʁeɡastɛl]; Breton: Tregastell) is a commune in the Côtes-d'Armor department of the region of Brittany in northwestern France.

Inhabitants of Trégastel are called trégastellois in French.

The municipality launched a linguistic plan through Ya d'ar brezhoneg in February 2008.

[5] Trégastel is twinned with: In 1892, Bruno Abakanowicz bought a small island called Costaérès in Trégastel, where by 1896 he had erected a neo-Gothic manor.

Since 1967, Trégastel has been home to a marine aquarium, built within a large, naturally occurring, outcrop of pink granite rocks.