Mazhabi Sikh, also known as Rangreta Sikhs, are a community from Northern India, especially Punjab region, who follow Sikhism. Mazhabi are part of wider category of Sikhs, who are of a Chuhra (Valmiki) caste background. The word Mazhabi is derived from the Arabic term Mazhab (meaning religion or sect), and can be translated as the faithful. They live mainly in Indian Punjab, Rajasthan and Haryana. The Mazhabi Sikhs and other Dalit Sikhs are often marginalized today by dominant Sikh castes, such as the Jats.

There are various terms to refer to this caste grouping based on religion, with them being known as Chuhras by Hindus, as Musalli or Kutana by Muslims, and as Mazhabis or Rangretas by Sikhs. Other terms are Bhangi or Mehta.

When Guru Tegh Bahadur, the ninth Sikh guru, was executed by the Mughals in Delhi, it is believed that a Mazhabi Sikh, named Bhai Jaita, recovered his dismembered body from a Muslim crowd and brought it back to his son, Guru Gobind Singh. In recognition of their act, he admitted the untouchables into the Khalsa (the Sikh faith), giving them the name Mazhabi ("faithful").

Mazhabis/Rangretas originate from Chuhra converts to Sikhism. Chuhras were the sweeping and scavenger caste in historical times. When they converted to Sikhism, they became known by new terms and often changed occupations. The Chuhras of Punjab were concentrated mostly in the eastern part of the Punjab Plains, especially in the Majha region, with their numbers being few west of Lahore, with notable exceptions being Rawalpindi, Multan, and Peshawar.

As per oral traditions, the Chuhras began converting to Sikhism more earnestly no later than during the period of the tenth Sikh guru, Guru Gobind Singh. One early account is of the tenth guru honouring a Chuhra Sikh, though in other accounts it was two brothers, who brought the head of Guru Tegh Bahadur to Anandpur from Delhi after much hardship. The conversion process of a Chuhra becoming a Sikh was simple, with them merely having "to assume the motto of Nanak Shah" (Nanak Shah ka mantra lana). The conversion process for Chuhras joining the Sikh religion involved a secret mantra, a communal feast of members of the same caste, and a prayer conducted by the sponsor for the candidate. Whilst some Chuhra Sikhs underwent the pahul baptismal ceremony to the Khalsa, there were varying degrees of adherence to established or ordained Sikh beliefs and practices, evolving over time, with some Chuhra Sikhs forgoing keeping kesh and participating in smoking, whilst others more strictly adhered to keeping kesh, wearing a kara, having a kanga, or keeping other articles of the Sikh faith. Some Chuhras outside of Punjab, such as in Poona and Benaras were also influenced by Sikhism. Aside from Hindu Chuhras and Sikh Chuhras, there were also Muslim Chuhras, with those whose ancestor(s) originally converting at an earlier historical period being known as Sekras or Sheikh Halalkhors, with those whose ancestor(s) converted at a latter time in history being known as Musalli, Kutana, or Dindar. Historically, conversions to Islam was usually a community-wide event, with entire caste-groups converting together, rather than on an individual basis.

Garja Singh, the companion of the 18th century martyr Bota Singh who was martyred alongside him, was a Rangreta Sikh.

During the colonial-era, the syncretic nature of the religious beliefs and practices of the Chuhras (mixing in aspects of Hinduism, Islam, and Sikhism) and their tendency to worship saints, was noted. Many Chuhras were originally followers of the cult of Lal Beg, known as the Lal Begi tradition. The colonial-era writers had a negative attitude to religious traditions they deemed as "syncretic", seeing them as impurities of organized religions and therefore not legitimate, instead of realizing that all religious traditions are ultimately syncretic fundamentally. Richard C. Temple stated the following on their religious customs:

This religion may be best styled hagiolatry pure and simple, as it consists merely of a confused veneration for anything and everything its followers, or rather their teachers, may have found to be considered sacred by their neighbours, whatever be its origin. Thus we find in the Panjab that in the religion of the scavenger castes the tenets of the Hindus, the Musalmans and the Sikhs are thrown together in the most hopeless confusion.