Trégastel (; ) is a commune in the Côtes-d'Armor department of the region of Brittany in northwestern France.
Trégastel is situated between Perros-Guirec and Pleumeur-Bodou. Lannion is away.
Inhabitants of Trégastel are called trégastellois in French.
The municipality launched a linguistic plan through Ya d'ar brezhoneg in February 2008.
In 2008, 16.5% of primary school children attended bilingual schools.
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.