An obligation is a course of action that someone is required to take, whether legal or moral. Obligations are constraints; they limit freedom. People who are under obligations may choose to freely act under obligations. Obligation exists when there is a choice to do what is morally good and what is morally unacceptable. There are also obligations in other normative contexts, such as obligations of etiquette, social obligations, religious, and possibly in terms of politics, where obligations are requirements which must be fulfilled. These are generally legal obligations, which can incur a penalty for non-fulfilment, although certain people are obliged to carry out certain actions for other reasons as well, whether as a tradition or for social reasons.

Obligations vary from person to person: for example, a person holding a political office will generally have far more obligations than an average adult citizen, who themselves will have more obligations than a child. Obligations are generally granted in return for an increase in an individual's rights or power.