Abdication is the act of formally relinquishing monarchical authority. Abdications have played various roles in the succession procedures of monarchies. While some cultures have viewed abdication as an extreme abandonment of duty, in other societies (such as pre-Meiji Restoration Japan), abdication was a regular event and helped maintain stability during political succession.

Historically, abdications have occurred both by force (where the regnant was dethroned, thus forced to abdicate on pain of death or other severe consequences) and voluntarily. Some rulers are deemed to have abdicated in absentia, vacating the physical throne and thus their position of power, although these judgements were generally pronounced by successors with vested interests in seeing the throne abdicated, and often without or despite the direct input of the abdicating monarch.

Recently, due to the largely ceremonial nature of the regnant in many constitutional monarchies, many monarchs have abdicated due to old age, such as the monarchs of Belgium, Denmark, Cambodia, the Netherlands, Spain, and Japan.

The word abdication is derived from the Latin abdicatio meaning to disown or renounce (ab, away from, and dicare, to proclaim). In its broadest sense abdication is the act of renouncing and resigning from any formal office, but it is applied especially to the supreme office of state. In Roman law the term was also applied to the disowning of a family member, such as disinheriting a son. Today the term is commonly only used for monarchs. An elected or appointed official is said to resign rather than to abdicate. A notable exception is the voluntary relinquishing of the office of Bishop of Rome (and thus sovereign of the Vatican City State) by the pope, called papal resignation or papal renunciation.

In certain cultures, the abdication of a monarch was seen as a profound and shocking abandonment of royal duty. As a result, abdications usually only occurred in the most extreme circumstances of political turmoil or violence. Likewise, when abdications were forced on an incompetent or tyrannical ruler, only the severest of circumstances would entail the risk in compelling it. The forced abdication may also be viewed as a vicious abuse of power by those who compel it.

For other cultures, abdication was a much more routine element of succession, often employed to smooth the transition process between monarchs.

Among the most notable abdications of antiquity are those of Lucius Quinctius Cincinnatus, the Roman dictator, in 458 and 439 BC; Lucius Cornelius Sulla, the Roman dictator, in 79 BC; Emperor Diocletian in AD 305; and Emperor Romulus Augustulus in AD 476.

Due to the complex nature of the office of pope (head of the worldwide Catholic Church and sovereign of the Papal States from 754 to 1870 and of Vatican City since 1929), a papal abdication involves both the spiritual and the secular sphere. Technically, the correct term for a reigning pope voluntarily stepping down as bishop of Rome is renunciation or resignation, as regulated in Canon 332 §2 of the 1983 Code of Canon Law.