Liberty is the ability to do as one pleases, or a right or immunity enjoyed by prescription or by grant (i.e. privilege). It is a synonym for the word freedom.

In modern politics, liberty is understood as the state of being free within society from control or oppressive restrictions imposed by authority on one's way of life, behavior, or political views. In theology, liberty is freedom from the effects of "sin, spiritual servitude, [or] worldly ties".

Sometimes liberty is differentiated from freedom by using the word "freedom" primarily, if not exclusively, to mean the ability to do as one wills and what one has the power to do; and using the word "liberty" to mean the absence of arbitrary restraints, taking into account the rights of all involved. In this sense, the exercise of liberty is subject to capability and limited by the rights of others. Thus liberty entails the responsible use of freedom under the rule of law without depriving anyone else of their freedom. Liberty can be taken away as a form of punishment. In many countries, people can be deprived of their liberty if they are convicted of criminal acts.

Liberty originates from the Latin word libertas, derived from the name of the goddess Libertas, who, along with more modern personifications, is often used to portray the concept, and the archaic Roman god Liber. The word "liberty" is often used in slogans, such as in "life, liberty, and the pursuit of happiness" and "Liberté, égalité, fraternité".