Langoat

La Roche-Derrien (French pronunciation: [la ʁɔʃ dɛʁjɛ̃]; Breton: Ar Roc'h-Derrien) is a former commune in the Côtes-d'Armor department of Brittany in northwestern France. On 1 January 2019, it was merged into the new commune La Roche-Jaudy.

La Roche-Jaudy (French pronunciation: [la ʁɔʃ ʒodi]; Breton: Roc'h-ar-Yeodi) is a commune in the Côtes-d'Armor department of Brittany in northwestern France. It was established on 1 January 2019 by merger of the former communes of La Roche-Derrien (the seat), Hengoat, Pommerit-Jaudy and Pouldouran.

Camlez (French pronunciation: [kamlɛs]; Breton: Kamlez) is a commune in the Côtes-d'Armor department of Brittany in northwestern France.

Pommerit-Jaudy (French pronunciation: [pɔmʁit ʒodi]; Breton: Peurid-ar-Roc'h) is a former commune in the Côtes-d'Armor department of Brittany in northwestern France. On 1 January 2019, it was merged into the new commune La Roche-Jaudy.

Quemperven (French pronunciation: [kɛ̃pɛʁvɛ̃]; Breton: Kemperven) is a commune in the Côtes-d'Armor department of Brittany in northwestern France.

Tréguier (French pronunciation: [tʁegje] ; Breton: Landreger) is a port town in the French department of Côtes-d'Armor, Brittany, northwestern France. It is the capital town of the province of Trégor.

Tréguier Cathedral (French: Cathédrale Saint-Tugdual de Tréguier) is a Roman Catholic church and former cathedral in Tréguier, Côtes-d'Armor, France. It is dedicated to Saint Tudwal. The church was formerly the seat of the Bishopric of Tréguier, abolished under the Concordat of 1801, when its territories were divided between the Diocese of Quimper and the Diocese of Saint-Brieuc, known since 1852 as Saint-Brieuc-Tréguier.

Plouguiel (French pronunciation: [pluɡjɛl] ; Breton: Priel) is a commune in the Côtes-d'Armor department of Brittany in northwestern France.

The former Breton and French diocese of Tréguier existed in Lower Brittany from about the sixth century, or later, to the French Revolution. Its see was at Tréguier, in the modern department of Côtes-d'Armor. The title continues in the contemporary diocese of Saint-Brieuc and Tréguier.

The canton of Tréguier is an administrative division of the Côtes-d'Armor department, northwestern France. Its borders were modified at the French canton reorganisation which came into effect in March 2015. Its seat is in Tréguier.It consists of the following communes: