Coordinates: 48°47′09″N 3°13′52″W / 48.7858°N 3.2311°W / 48.7858; -3.2311

Tréguier (Breton: Landreger) is a port town in the Côtes-d'Armor department in Brittany in northwestern France. It is the capital of the province of Trégor.

Tréguier is located 36 m. N.W. of Saint-Brieuc by road. The port is situated about 5½ m. from the English Channel at the confluence of two streams that form the Tréguier River.

Tréguier (Trecorum), which dates from the sixth century, grew up round a monastery founded by Saint Tudwal (died c. 564). In the 9th century it became the seat of a bishopric, suppressed on July 12, 1790 (decree of November 14, 1789). Pop. (1906), 2605.

Inhabitants of Tréguier are called trécorrois.

In 2008, 11.78% of primary school children attended bilingual schools.

The cathedral, remarkable in having three towers over the transept, one of which is surmounted by a fine spire, dates from the 14th and 15th centuries. It contains the sumptuous modern mausoleum of Ivo of Kermartin (St Yves; d. 1303), a canon of the cathedral and patron saint of lawyers. The building of the cathedral was largely due to him. The Pardon of Saint Ivo, a religious festival, attracts an international audience drawn from the legal profession. To the south of the church there is a cloister (1468) with graceful arcades.