The Banishment Act or Bishops’ Banishment Act, which receives royal assent on September 25, 1697, requires most Catholic clergy to leave the kingdom by May 1, 1698, and bans Catholic clergy from entering the kingdom. The Act is never efficiently enforced.

The Banishment Act is a 1697 Act of the Parliament of Ireland which banishes all ordinaries and regular clergy of the Roman Catholic Church from Ireland. All “popish archbishops, bishops, vicars general, deans, jesuits, monks, friars, and other regular popish clergy” are required to be in one of several named ports awaiting a ship out of the country by May 1, 1698. Remaining or entering the country after this date would result in punishment as a first offence with twelve months imprisonment followed by expulsion. A second offence would constitute high treason.

The Act is one of the Penal Laws passed after the Williamite War to safeguard the Church of Ireland as the established church and from fears of Catholic clerical support for Jacobitism. It is foreshadowed by proclamations issued by the Dublin Castle administration in 1673 and 1678 with similar terms. The banishment is originally and most effectively applied to regular clergy, many of whom register under the Registration Act of 1704, as parish priests to be treated as secular clergy and avoid deportation. The ban on bishops may have been intended to prevent ordination of new priests, which, coupled with a ban on clerical immigration, would lead to their eventual extinction. Of the eight Catholic bishops in Ireland when the act is passed, two leave, one (John Sleyne)is arrested, and five go into hiding. The port authorities pay for the passage of 424 clerics who emigrate. Mary of Modena estimates that about 700 in total leave, of whom 400 settle in France. Priest hunters are active in subsequent decades. Maurice Donnellan, Bishop of Clonfert, is arrested in 1703 but rescued by an armed crowd.

The Act is gradually less stringently enforced as the eighteenth-century progresses. The Roman Catholic Relief Act 1782 provides that its provisions cannot apply to a priest who has registered and taken the oath of supremacy. The Act is explicitly repealed by the Statute Law Revision (Ireland) Act 1878.