Karma, originating in ancient India, is a principle of cause and effect that links an individual's actions and intentions to their future consequences. This concept is central to several Indian religions, including Hinduism, Buddhism, Jainism, and Sikhism, often intertwined with the idea of rebirth (samsara). While good intentions and deeds are believed to lead to positive outcomes and happier future lives, negative ones result in less favorable circumstances. The principle is not universally understood as fate or destiny, which have distinct terms in Sanskrit. Different traditions and schools within these religions offer varied interpretations and emphasize different aspects of karma, leading to a complex and multifaceted understanding of the concept. Some interpretations highlight its ethical dimension, while others focus on its psychological impact and habit formation.

The principle of karma, often referred to as the law of karma or karma-theory, is fundamentally about causality. It posits that actions, both physical and intentional, generate consequences. This causality can be ethical or non-ethical, but a common understanding is that good actions and intentions yield positive results, while bad ones lead to negative outcomes. This ethicization means that an individual's present circumstances can be understood as a result of past actions, whether from the current life or previous ones. The law of karma is understood to operate independently of any divine judgment. Furthermore, karma is seen as a psychological force, shaping habits and self-perception, thereby influencing an individual's experience and the course of their life. Breaking negative habits, according to this view, requires conscious karmic effort.

A significant aspect of karma, particularly in Hinduism, Buddhism, Jainism, and Sikhism, is its connection to the cycle of rebirth, known as samsara. In these traditions, karma influences the nature and quality of future lives. The accumulation of karmic impulses from one life is believed to carry over into the next, determining the realm, condition, and form of subsequent existences. This cycle continues until individuals achieve liberation (moksha) by consciously breaking free from karmic influences. However, the necessity and interpretation of rebirth in relation to karma have been subjects of debate within ancient Indian literature, with some schools considering it essential, others secondary, and a few viewing it as flawed.

The concept of karma is not monolithic; its meaning, importance, and scope vary significantly across different traditions and schools of thought that originated in India. For instance, while some Hindu traditions classify karma into types like accumulated (Sanchita), bearing fruit (Prārabdha), and future (Āgāmi/Kriyamāṇa), others may link karma directly to rebirth while some consider karma essential but not rebirth. Scholars continue to debate whether karma is best understood as a theory, a model, a metaphor, or a metaphysical stance. In contemporary contexts, New Age beliefs often incorporate karma as a law of cosmic balance, emphasizing cause and effect without necessarily framing it as a system of punishment.