Independent Catholicism is an independent sacramental movement of clergy and laity who self-identify as Catholic (most often as Old Catholic or as Independent Catholic) and form "micro-churches claiming apostolic succession and valid sacraments", in spite of not being affiliated with the Catholic Church. The term "Independent Catholic" derives from the fact that "these denominations affirm both their belonging to the Catholic tradition as well as their independence from Rome".

It is difficult to determine the number of jurisdictions, communities, clergy and members who make up Independent Catholicism, particularly since the movement "is growing and changing in every moment". Some adherents choose Independent Catholicism as an alternative way to live and express their Catholic faith outside the Catholic Church (with whose structures, beliefs and practices Independent Catholicism often closely aligns) while rejecting some traditional Catholic teachings.

Independent Catholicism may be considered part of the larger independent sacramental movement, in which clergy and laity of various faith traditions—including the Eastern Orthodox Church, the Lutheran churches, the Anglican Communion and various non-Catholic Christian churches—have separated themselves from the institutions with which they previously identified. Within this movement, various independent churches have sprung from the Eastern Orthodox Church, but the members of these independent Eastern Orthodox groups most often self-identify as independent or autocephalous Orthodox and not as Independent Catholic.

Some Independent Catholic churches have joined the International Council of Community Churches, a denomination based in Loudon, Tennessee, in the United States. In doing so, it gives them a place and voice in national and international Christian organizations such as Churches Uniting in Christ, the National Council of Churches of Christ in the USA and the World Council of Churches, membership of which is usually reserved to larger, longer-established church bodies.

The consecration of bishops without the approval of the wider church or papal mandate appears to be an ancient phenomenon, which led to Canon VI of the Council of Chalcedon's assertion that any potential sacramental validity of such consecrations is valueless without the church's endorsement. The resurgence of the phenomenon in the modern era seems to have coincided with the spread of Enlightenment values. Beginning in 1724, Dominique Marie Varlet (1678–1742), the Latin Catholic Bishop of Babylon, consecrated four men successively as Archbishop of Utrecht without papal approval.

This consecration by Varlet caused a theological controversy and schism within the Catholic Church, which now possessed bishops who were validly consecrated without the permission of the pope. This schism marked the birth of the movement that would later be known as the Old Catholic Church (a term coined in 1853 for the Catholics of Utrecht).

The sharing of apostolic succession in the west outside the Catholic Church was largely confined to the Church of Utrecht for over a century. After the (First) Vatican Council in 1870, many Austro-Hungarian, German and Swiss Catholics rejected assertions of universal jurisdiction of the pope and the declaration of papal infallibility, and their bishops, inspired by earlier acts in Utrecht, decided to leave the Catholic Church to form their own churches, independent of Rome. Now independent of the Pope, these bishops were sometimes referred to as autocephalous (or self-governing) bishops from within their circles or episcopi vaganti (wandering bishops) from outside of their circles. These validly-consecrated bishops could claim apostolic succession, and they continued to share valid lines of apostolic succession with the priests and deacons they ordained. In 1889, they formally united as part of the Utrecht Union of Churches (UU).

In 1908, the movement that would become Independent Catholicism left continental Europe when Arnold Harris Mathew (1852–1919), a former Catholic priest, was consecrated in Great Britain by Archbishop Gerardus Gul (1847–1920) of the Old Catholic Church of the Netherlands. Mathew believed that Old Catholicism might provide a home for disaffected Anglican clergy who reacted to Pope Leo XIII's declaration that Anglican orders were null and void, and Gul incorrectly believed that Mathew had a significant following in the United Kingdom. Two years later, in 1910, Mathew consecrated two priests to the episcopate, without clear reasons and without consulting the Archbishop of Utrecht, and, in response to the ensuing protest, declared his autonomy from the Old Catholic Church. Mathew later consecrated several other bishops who spread through England and North America. Plummer writes that, as a result, "we begin to see the small, endlessly multiplying groups, with a high percentage of the membership in holy orders, which came to characterize the independent movement."