A convent founded in 1204, 8 m. SW. of Versailles, and which in the 17th century became the head-quarters of Jansenism, and the abode of Antoine Lemaitre, Antoine Arnauld, and others, known as the "Solitaires of the Port Royal." They were distinguished for their austerity, their piety, and their learning, in evidence of which last they established a school of instruction, in connection with which they prepared a series of widely famous educational works.