The Third Order of Saint Dominic (properly referred to as the Lay Fraternities of St Dominic or Lay Dominicans since 1972) is a Roman Catholic third order affiliated with the Dominican Order.
Lay Dominicans are men and women, singles and couples living a Christian life with a Dominican spirituality in the secular world. They find inspiration following the same spiritual path taken by many saints, blessed, and other holy men and women throughout the almost 800-year history of the Dominican Order. The Life of a Dominican layperson is all about having a passion for the Word of God. It is about committing one self to a community of like minded brothers and sisters that immerse themselves in the Word of God. There are Lay Dominican Provinces all around the world.
This was one of the earliest developments of the ancient Ordo de Poenitentia (Order of Penance). This was a status which developed in the ancient Church, in which those faithful who sought a more dedicated way of life embraced the lifestyle of a penitent then in effect in the Church. It was not the organization from which the Friars Preachers evolved, but rather represents that portion of the Order of Penance which came under Dominican influence. At first vaguely constituted and living without system or form, its members gradually grew more and more dependent on their spiritual guides.
The climax was reached, and the work of St. Dominic received its final perfection, when Friar Munio of Zamora, the seventh Master General of the Friars Preachers, formulated a definite Rule in 1285. By this the Ordo de Poenitentia was to be ruled in each local centre by a Dominican priest and was to be subject to the obedience of the Dominican priors provincial and Masters General. No longer were there to be any of those vague transitions and extravagant vagaries which disfigured in history these Orders of Penance. Henceforward this branch was linked to the fortunes of the Friars Preachers, wore their habits of black and white (with few minor differences varying according to time and country), and was to participate in all their good works. They were not called a third order indeed until after the 13th century but continued to be known as "Brothers and Sisters of Penance" with the addition "of St. Dominic", that is say, they were the "Brothers and Sisters of Penance of St. Dominic".