The Order of Preachers (Latin: Ordo Praedicatorum, hence the abbreviation OP used by members), more commonly known after the 15th century as the Dominican Order or Dominicans, is a Roman Catholic religious order founded by the Spanish priest Saint Dominic de Guzman in France, and approved by Pope Honorius III (1216–27) on December 22, 1216.

Membership in the Order includes friars, nuns, active sisters, and lay or secular Dominicans (formerly known as tertiaries) affiliated with the Order.Founded to preach the Gospel and to combat heresy, the teaching activity of the order and its scholastic organization places the Preachers in the forefront of the intellectual life of the Middle Ages.

The Dominican Order is headed by the Master of the Order.

Members of the order generally carry the letters O.P., standing for Ordinis Praedicatorum, meaning of the Order of Preachers, after their names.In the year 2000, there are 5,171 Dominican friars in solemn vows, 917 student brothers, and 237 novices.

[4] By the year 2010 there were 5,906 Dominican friars, including 4,456 priests.

A number of other names have been used to refer to both the order and its members.

Their identification as Dominicans gives rise to the pun that they were the Domini canes, or Hounds of the Lord.

In England and other countries the Dominican friars are referred to as Black Friars because of the black cappa or cloak they wear over their white habits.

Dominicans are Blackfriars, as opposed to Whitefriars (for example, the Carmelites) or Greyfriars (for example, Franciscans).

They are also distinct from the Augustinian Friars (the Austin friars) who wear a similar habit.

In France, the Dominicans are known as Jacobins, because their convent in Paris was attached to the church of Saint-Jacques, now disappeared, on the way to Saint-Jacques-du-Haut-Pas, which belonged to the Italian Order of San Giacomo dell Altopascio (St. James) Sanctus Jacobus in Latin.