Antidisestablishmentarianism is a political philosophy that is opposed to the separation of church and state. The term originated in the context of the nineteenth century Church of England, where "antidisestablishmentarians" were opposed to proposals to remove its status as the state church of England. Antidisestablishmentarianism succeeded in England, but failed in Ireland and Wales, with the Church of Ireland being disestablished in 1871 and the Church in Wales in 1920. The term has largely fallen into disuse, although the issue itself is still current (see Act of Settlement 1701).

Though not strictly true, the word antidisestablishmentarianism is often quoted as being one of the longest English words that has an actual meaning (as opposed to words that were made up for the purpose of being long).

See also

• Disestablishmentarianism
• Religion in the United Kingdom
• Welsh Church Act 1914