Saint Pompeia (in Latin: Alma Pompeia or in Breton: Koupaia ^[1]), also known as Aspasia, is a legendary Breton saint who supposedly lived in the 6th century. Her feast day is celebrated on 2 January.

According to the life of her son, Tudwal, Pompeia was the sister of King Riwal II of Domnonée.^[2] Tradition at Langoat further asserts that she became one of the wives of the fictional King Hoel Mawr (or the Great) who was invented by Geoffrey of Monmouth as a supposed overlord of all Brittany.^[3] After being exiled in Britain for some years, Pompeia eventually returned to her husband's kingdom with her daughter, Saint Scaeva, and her son, Saint Tudwal.^[2] She settled near the monastery of Tréguier, founded by the latter, and died where the church of Langoat stands today.^[2] Her relics are still preserved there and a shrine has been erected to her memory.

Saint Pompeia was the mother of:

• Saint Tudwal: one of the seven founding saints of Brittany
• Sainte Scaeva
• Saint Leonorus

• Langoat: Saint Pompeia's Church in the shape of a Latin cross stands there. Inside is the shrine said to be of Saint Pompeia and bas-relief panels recounting her legend.
• Sainte-Sève: Saint Scaeva's Church there contains a statue of Saint Pompeia; the name of the locality, Trébompé, probably stems from a corruption of the name Pompeia.
• Valley of the Saints: A statue of Saint Pompeia sculpted by P. Le Guen and P. Leost in blue granite from Lanhelin, was erected in 2012.
• Trézény: There is a stained glass window representing Saint Pompeia in the Saint Zény's Church.