[3] Tréguier (Trecorum), which dates from the sixth century, grew up round a monastery founded by Saint Tudwal (died c. 564).

[6] Count Stephen of Tréguier was the second Earl of Richmond, inheriting the British peerage created by William the Conqueror for his second cousin Alan Rufus.

The United States Navy established a naval air station on 1 November 1918 to operate seaplanes during World War I.

It contains the sumptuous modern mausoleum of Ivo of Kermartin (St Yves; died 1303), a canon of the cathedral and patron saint of lawyers.

[3] The Pardon of Saint Ivo, a religious festival, attracts an international audience drawn from the legal profession.

[3] As he was a prominent skeptic, author of the "pagan" Prayer on the Acropolis, the 1903 unveiling of Renan's statue, which also included a depiction of the goddess Athena, led to widespread protests from the Catholic Church.