Caste (vaõõa) is the Hindu belief that humans were created by Brahma as four distinct and different types; priests (bràhmaõa), warriors (khattiya), merchants (vessa) and labourers (sudda). According to this belief, the different castes are required make their living in different ways, should not mix and should be treated differently. Beyond the four castes are the outcastes (nãcàkulà or vasala) and foreigners (milakkha), those who have no caste and are considered beyond the pale of ordinary Hindu society. Brahmins believed in and taught the idea that “brahmins are the highest caste, other castes are inferior; brahmins are fair, other castes are dark; only brahmins are pure, non-brahmins are impure” (M.II,148)

The Buddha was an outspoken critic of caste and at least a dozen of his discourses are devoted to highlighting its contradictions and cruelties. His own tribe, the Sakyans, were excessively proud of their high caste status. When a group of them requested to become monks, the Buddha ordained Upàli, a low caste barber, first, thus giving him a precedence that would require the others to bow to him (Vin.II,183). The only social division the Buddha accepted was that of householder (gahapati) and homeleaver (pabbajita), i.e. monks and or nuns. Neither of these states are determined by any innate quality but by one's lifestyle and life-goal, and rather than being fixed, like caste, a person could choose to move from one to another.   

The Buddha criticised the caste system on several grounds. The claim that it was ordained by a supreme being is no more than a myth (M.II,148). Caste is not practised everywhere and thus must be a regional custom rather than a universal truth (M.II,149). The claim that different castes have different abilities and personalities is not born out by experience and is thus invalid (M.II,150; Sn.116). Low castes and outcastes may be dirty because they are compelled to do dirty jobs, but if they wash themselves they become as clean as everyone else (M.II,151). The caste system engenders cruelty and suffering and is thus evil.

The Buddha further pointed out that the supposed divine origin of caste differences is even contradicted by economic realities. If an outcast managed to become wealthy he could employ a desperately poor brahmin and compel him to wait on him, serve him, and do his bidding (M.II,85). From the Buddhist perspective, how people are treated, the respect they receive, the opportunities they have, even where they are reborn, should depend on their behaviour, not what caste they are born into. The Buddha said: `Without righteousness, all castes can go to purgatory. All castes are pure if they act with righteousness'(Ja.VI,100).

The Buddhist critique of caste took many forms and lasted for many centuries. In the Divyàvadàna there is a story about an outcaste woman whom the Buddha ordained as a nun, to the horror and anger of the upper caste citizens of Sàvatthi. The Buddha is then portrayed as giving these citizens a series of arguments as to why caste is invalid. The most interesting of these arguments is that one could have been high caste, low caste or outcaste in one's former life or that one might be in the next life, and that one's future is conditioned by one's behaviour in this life (i.e. kamma), not by which caste one belongs to.

Despite the Buddha's repudiation of caste, more mild and flexible variations of the system exist in most Buddhist countries. The paya kyun of Burma are the descendants of monastery slaves, and the buraku of Japan and the ragyapa of Tibet, were originally degraded because they worked as fishermen, scavengers or butchers. These groups are marginalized by their respective societies. Sri Lanka's monastic sects are all divided along caste lines. Since the 1950s, millions of low caste and outcaste people in India, following the example of their leader Dr. Ambedkar, have converted to Buddhism to escape the indignities of the Hindu caste system.