The abolition of monarchy and anti-royalism is a legislative or revolutionary movement to abolish monarchical elements in government, usually hereditary.

Abolition of absolutist monarchy in favor of limited government under constitutional monarchy is a less radical form of anti-royalism that has succeeded in some nations that still retain monarchs, such as the United Kingdom, Spain, Thailand.

Abolition has been carried out in various ways, including via abdication leading to the extinction of the monarchy, legislative reform, revolution, coup d'état, and decolonisation. Abolition became more frequent in the 20th century, with the number of monarchies in Europe falling from 22 to 12 between 1914 and 2015, and the number of republics rising from 4 to 34. Decolonisation and independence have resulted in an abolition of monarchies in a number of former colonies such as those created by the United Kingdom.

Motivations for abolition include egalitarianism and anti-class views, eliminating a rival system potentially opposed to another incoming system (as had occurred in Romania in 1947), opposition to undemocratic and hereditary institutions, perception of monarchy as anachronistic or outdated, and opposition to a particular monarch or dynasty. In many colonies and former colonies, abolishing the influence of the monarchy of a colonising state is considered part of decolonisation. In many Commonwealth realms, the monarchy may be viewed as a foreign institution running counter to the national identity or national sovereignty.

In the 21st century, some countries that are monarchies have significant republican movements, such as Spain and Australia.

Since the beginning of the 20th century, restorations of monarchies have been comparatively rare. Examples are the monarchy of Spain, which since 1947 had been nominally a regency with a vacant throne but the Bourbon dynasty was restored in 1975; the reinstatement in 1991 of the Emir of Kuwait following abolition in 1990 and the Gulf War; and a 1993 transition of Cambodia from a Marxist-Leninist republic to an elective monarchy.