List of Breton saints
Breton saints refers to one of two groups, the innumerable people who lived, died, worked in, or came to be particularly venerated in the nine traditional dioceses of Brittany (Cornouaille, Dol, Léon, Nantes, Rennes, Saint-Brieuc, Saint-Malo, Tréguier, Vannes) who were accepted as saintly before the establishment of the Congregation of Rites (now the Congregation for the Causes of Saints), or those saints, blesseds, venerables, and Servants of God who have come to be recognized since that time.
Breton saints refers to one of two groups, the innumerable people who lived, died, worked in, or came to be particularly venerated in the nine traditional dioceses of Brittany (Cornouaille, Dol, Léon, Nantes, Rennes, Saint-Brieuc, Saint-Malo, Tréguier, Vannes) who were accepted as saintly before the establishment of the Congregation of Rites (now the Congregation for the Causes of Saints), or those saints, blesseds, venerables, and Servants of God who have come to be recognized since that time.

Armorican saints
Before the Bretons came, the land now known as Brittany was known as Armorica within the Roman province of Gallia Lugdunensis. The earliest saint associated with this region is Anne, mother of Mary (mother of Jesus), said by tradition to have been Armorican, and she is the patroness of Brittany. She also appeared to Yves Nicolazic, to whom she spoke in Breton.
After her, the earliest saints in what is now Brittany have dates which are sometimes unclear, but tradition holds they go back to the earliest days of the church. Maxime, said to have been the disciple of Philip the Apostle, was sent to preach among the Gauls and was made the first Bishop of Rennes. He may have been accompanied by saints by the names of Clarus and Justus.  Pope Linus, the second Bishop of Rome, sent Clair and Adeodatus; this is said to be Clair who became the first Bishop of Nantes around AD 280 and died early in the third century, though the dates make this suspect, and Adeodatus preached especially in the area of Vannes.  Other Armorican saints include Similien, the third Bishop of Nantes in the early fourth century, and the brother-martyrs Donatian and Rogatian.  Palladius may also have had an Armorican connection.

The Seven Founders
The Bretons, coming from the British Isles, brought Christianity with them.  With the coming of the Bretons, the seven ancient dioceses were established by the seven founding saints.

Tudwal founded Tréguier
Pol Aurelian founded Saint-Pol-de-Leon
Brioc founded Saint-Brieuc
Malo founded Saint-Malo
Patern founded Vannes
Corentin founded Cornouailles
Samson founded DolThe other two dioceses of Brittany were founded by Clair de Nantes and Maxime de Rennes.

Medieval saints
Monarchs
Darerca, Queen of Brittany
Judicael, Breton king
Salomon, King of Brittany

Bishops
Others
Modern saints
The "modern" in modern saints refers to the process, not the person, and groups those whose status has been recognized by Rome.

Saints
Benedetto Menni, priest, canonized in 1999
Gohard of Nantes, Bishop, canonized in 1096
Louis de Montfort, priest, canonized in 1947
Marie of the Cross (Jeanne Jugan), religious, canonized in 2009
Mother Theodore, religious, canonized in 2006
Vincent Ferrer, Dominican priest, canonized in 1455
William Pinchon, Bishop, canonized in 1247
Yves Helory, priest, canonized in 1347
Of the One Hundred Twenty Martyrs of China
Marie of Saint Natalie (Jeanne-Marie Guerguin)
Marie of Saint Just (Anne-Françoise Moreau)

Blesseds (by beatification)
Cassien of Nantes, Capuchin, beatified in 1905
Charles of Blois, duke, beatified in 1904
Julian Maunoir, Jesuit priest, beatified in 1951
Marcel Callo, layman, beatified in 1987
Mary of the Passion, religious, beatified in 2002
Marie-Louise-Élisabeth de Lamoignon, religious, beatified in 2012
Pierre-Rene Rouge, Vincentian priest, beatified in 1934
Of the Twenty Martyrs of Capuchin Tertiary Fathers and Brothers of Our Lady of Sorrows in Spain, beatified in 2001
Carmen Marie Anne Garcia Moyon
Of the Fifteen Martyrs of the Daughters of Charity of Saint Vincent de Paul and the Ursulines of Valenciennes (of the Martyrs of the French Revolution, beatified in 1920
Therese-Madeleine Fantou
Of the One Hundred Ninety-One Martyrs of the September Massacres, beatified in 1926
Charles-Francois le Gue
Claude-Antoine-Raoul Laporte
Francois-Hyacinth le Livec de Tresurin
Henri-August Luzeau de la Mulonniere
Jean-Charles-Marie Bernard du Cornillet
Joseph Becavin
Louis-Laurent Gaultier
Mathurin-Nicolas de la Villecrohain le Bous de Villeneuve
Nicolas-Marie Verron
Rene-Joseph Urvoy
Rene-Julien Massey
Rene-Marie Andrieux
Vincent-Joseph le Rousseau de Rosencoat
Yves-Andre Guillon de Keranrun
Yves-Jean-Pierre Rey de Kervisic
Of the Fifteen Martyrs of Laos
Jean-Baptiste Malo
Joseph Boissel
Vincent L'Henoret
Of the Nineteen Martyrs of Algeria
Alain Dieulangard
Celestin Ringeard
Michel Fleury

Blesseds (by confirmation of cult)
David, cult confirmed in 1120
Françoise d'Amboise, cult confirmed 1863
John of the Grating, Cistercian Bishop, cult confirmed in 1517
Yann Divotou, Franciscan priest, cult confirmed in 1989
Ralph de la Futaye, unclear when cult confirmed

Venerables
Alain-Marie Guynot de Boismenu, religious Bishop, proclaimed in 2014
Jean-Marie Robert de la Mennais, religious priest, proclaimed in 1966
Marie-Amelie Fristel, religious, proclaimed in 1976
Michel le Nobletz, priest, proclaimed in 1915

Servants of God
Louis-Marie Leveil
Louis de Goesbriand
Alano Maria du Noday
Catherine de Francheville
Claude-Francois Poullart des Places
Francois-Marie-Benjamin Richard de la Vergne
Jacques Cathelineau
Jean of Saint Samson
Marie-Yvonne-Aimee of Jesus
Pauline-Louise Pinczon du Sel
Pierre Quintin
Pierre-Joseph Picot de Cloriviere
Robert of Arbrissel
Simon Brute
Victor Lelievre
Yves Nicolazic (Ivon Nikolazig in Breton)
Of the Fifty Martyrs of France of the Apostolate Within the Service du Travail Obligatoire
Eugene Lemoine
Maurice-Philippe Bouchard
Roger (Paul) le Ber
Of the Thirty-Eight Martyrs of the Revolutionary Tribunal of Paris
Francois-Georges Cormaux
Therese Guillaudeu du Plessis
Victoire Conen de Saint-Luc
The Eighty-Five Martyrs of Rennes of the French Revolution

Other saintly Bretons
Corentin Cloarec, killed by the Nazis
Joachim Nio, killed by the Gestapo

See also
List of Welsh saints, many of whom shared Breton connections.
List of saints of the Canary Islands

References
"The Catholic Encyclopedia"
"Hagiography Circle"
M. de Garaby, Vie des bienheureux et des saints de Bretagne, éd. J.-M. Williamson, Nantes, 1839. Réédition 1991.
P.T. de S. Luc, C.  L'Histoire de Conan Mériadec Qui Fait le Premier regne de l'histoire generale des souverains de la Bretagne Gauloise, dite Armorique. Paris, 1664.