Shudra or Shoodra (Sanskrit: Śūdra) is one of the four varnas of the Hindu class and social system in ancient India. Some sources translate it into English as a caste, or as a social class. Theoretically, Shudras constituted a class like workers.

According to Richard Gombrich's study of Buddhist texts, particularly relating to castes in Sri Lankan Buddhist and Tamil Hindu society,

"The terms Vaisya and Sudra did not correspond to any clear-cut social units, even in the ancient period, but various groups were subsumed under each term [...]; In medieval times (say AD 500–1500) though society was still said to consist of the four classes, this classification seems to have become irrelevant[.]"

The word Shudra appears in the Rigveda and it is found in other Hindu texts such as the Manusmriti, Arthashastra, dharmaśāstras and jyotiḥśāstras. In some cases, Shudras participated in the coronation of kings, or were amatya "ministers" and rajas "kings" according to early Indian texts.

The term śūdra appears only once in the Rigveda. This mention is found in the mythical story of creation embodied in the Puruṣasuktam. It describes the formation of the four varnas from the body of a primeval man. It states that the brahmin emerged from his mouth, the kshatriya from his arms, the vaishya from his thighs and the shudra from his feet. According to historian Ram Sharan Sharma, the purpose of this verse may have been to show that shudras had the same lineage as the other varnas and hence were a section of society in the Vedic period. On the other hand, it could also represent an attempt to provide a common mythical origin for the heterogenous Brahminical society.

While the Rigveda was most likely compiled between c. 1500 BCE and 1200 BCE, John Muir in 1868 suggested that the verse that mentions the four varnas has "every character of modernness both in its diction and ideas". The Purusha Sukta verse is now generally considered to have been inserted at a later date into the Vedic text, possibly as a charter myth.

According to Stephanie W. Jamison and Joel Brereton, "there is no evidence in the Rigveda for an elaborate, much-subdivided and overarching caste system", and "the varna system seems to be embryonic in the Rigveda and, both then and later, a social ideal rather than a social reality". Historian Ram Sharan Sharma states that "the Rig Vedic society was neither organized on the basis of social division of labour nor on that of differences in wealth... [it] was primarily organised based on kin, tribe and lineage."

According to Sharma, nowhere in the Ṛgveda or Atharvaveda "is there any evidence of restrictions regarding food and marriage either between the Dasa and Aryan, or between the Shudra and the higher varnas". Further, adds Sharma, in late Atharva Veda, "Shudra does not come in for notice, probably because his varna did not exist at that stage".