For alternate uses, see Affirmation (disambiguation).

An affirmation (from Latin affirmare, to assert) is the declaration that something is true.

In logic, an affirmation is a positive judgment, the union of the subject and predicate of a proposition.

In law, an affirmation is a solemn declaration allowed to those who conscientiously object to taking an oath. An affirmation has exactly the same legal effect as an oath, but is usually taken to avoid the religious implications of an oath. The Constitution of the United States makes four references to an "oath or affirmation": In Article I, Senators must take a special oath or affirmation for the purpose of sitting as the tribunal for impeachment; in Article II, the president is required to take a specified oath or affirmation before entering office (see oath of office); in Article VI, all state and federal officials must take an oath or affirmation to support the U.S. Constitution; and in Amendment IV, all search warrants must be supported by evidence given under oath or affirmation.

In spirituality and personal development, an affirmation is a form of autosuggestion in which a statement of a desirable intention or condition of the world or the mind is deliberately meditated on or repeated in order to implant it in the mind. It could be viewed as a kind of self-induced brainwashing and is similar to the way a mantra works in forms of meditation called Samadhi. Affirmations can be a very powerful means of reprogramming the unconscious mind.

Perhaps the most often used and well-known affirmation is the word "Amen," which can be translated simply, "so be it," affirming the truth of whatever was written or said immediately prior. While often used to conclude prayer, the word itself is neutral as to its context and exemplifies a logical affirmation more than a spiritual one.