The Fraticelli (Italian for “Little Brethren”) or Spiritual Franciscans opposed changes to the rule of Saint Francis of Assisi, especially with regard to poverty, and regarded the wealth of the Catholic Church as scandalous, with the riches of individual churchmen as invalidating their status^{[citation needed]}. The Fraticelli were declared heretical in 1296 by Boniface VIII.

The name Fraticelli is used for various sects, which appeared in the thirteenth, fourteenth and fifteenth centuries, principally in Italy, that split from the Franciscan Order on account of the disputes concerning poverty. It is necessary to differentiate the various groups of Fraticelli, although the term may be applied to all. The main groups were the Fraticelli de Paupere Vita and the Fraticelli de Opinione (also called Michaelites).

The Apostolics (also known as Pseudo-Apostles or Apostolic Brethren) are excluded from the category, because admission to the Order of Saint Francis was expressly denied to their founder, Gerard Segarelli. The Apostolics had no connection to the Franciscans, in fact desiring to exterminate them.

Umberto Eco's novel The Name of the Rose is set against the persecution of Fraticelli.

Fraticelli is a diminutive of the Italian frate (plural frati), itself derived from Latin Frater “brother”, often shortened to Fra when referring to members of religious orders.

Frati was a designation of the members of the mendicant orders founded during the thirteenth century, principally the Franciscans. The Latin Fraterculus does not occur in the old records which concern the Fraticelli. Etymologically, the name Friars Minor (Fratres Minores) is equivalent to the diminutive Fraticellus. The ideal of the founder of the Friars Minor, Saint Francis of Assisi, was that his disciples, by evangelical poverty, complete self-denial, and humility, should lead the world back to Jesus Christ. The Italian people designated as Fraticelli all the members of religious orders (particularly mendicants), and especially hermits, whether these observed monastic precepts or regulated their own lives.

Early Franciscans were itinerant preachers, who, following their founder Francis of Assisi, took to heart Christ's injunction in Luke 9:3: “Take nothing for the journey – no staff, no bag, no bread, no money, no extra shirt.” Living by such a rule required constant begging for alms, and over time this produced tensions, both with potential benefactors faced with repeated appeals from mendicant friars, and with established monastic orders accustomed to aid from the same pool of benefactors.

Over time, as the order grew, it faced the demands of caring for sick or elderly friars, and providing for its members sent to university for theological training. The order divided into two branches, the Zelanti, or Spirituals, and the Relaxati, known later as the Conventuals. The Zelanti strictly observed the poverty enjoined by the testament of Saint Francis, and lived isolated, simple lives. The Relaxati or Conventuals lived in convents in the towns, tending attached churches with the necessary liturgical furnishings and devoting themselves also to studying and preaching, which required the accumulation and use of books.