The Dulcinians were a religious sect of the Late Middle Ages, originating within the Apostolic Brethren. The Dulcinians, or Dulcinites, and Apostolics were inspired by Franciscan ideals and influenced by the Joachimites, but were considered heretical by the Catholic Church. Their name derives from the movement's leader, Fra Dolcino of Novara (ca. 1250–1307), who was burned as a heretic on the orders of Pope Clement V.
The Dulcinian sect began in 1300 when Gherardo Segarelli, founder of the Apostolic Brethren, was burned at the stake in Parma during a brutal repression of the Apostolics. His followers went into hiding to save their lives. Fra Dolcino had joined the Apostolics between 1288 and 1292, and became their leader. He published the first of his letters explaining his ideas about the epochs of history based on the theories of Gioacchino da Fiore.
Fra Dolcino, at the beginning of 1303, reunited the Apostolic movement near Lake Garda. He met Margaret of Trento (real name Margherita Boninsegna, his lover or sister in spirit), and wrote the second letter to the Apostolics. At the beginning of 1304, three Dulcinians were burned by the Inquisition, leading Dolcino to evacuate the community to the west side of the Sesia valley, near his native Novara. At the end of 1304, only 1400 survived on the top of Mount Parete Calva, in the fortified Piano dei Gazzari. They descended the mountain to pillage and kill the people in the valley, responsible in their eyes for not defending the group against the Episcopal troops. The villagers called them "Gazzari" (Cathars), and joined the soldiers in opposition.