The Nipmuc or Nipmuck people are an Indigenous people of the Northeastern Woodlands, who historically spoke an Eastern Algonquian language, probably the Loup language. Their historic territory Nippenet, meaning 'the freshwater pond place', is in central Massachusetts and nearby parts of Connecticut and Rhode Island.

The Nipmuc Tribe had contact with traders and fishermen from Europe prior to the colonization of the Americas. The first recorded contact with Europeans was in 1630, when John Acquittamaug (Nipmuc) took maize to sell to the starving colonists of Boston, Massachusetts. After the colonists encroached on their land, negotiated fraudulent land sales and introduced legislation designed to encourage further European settlement, many Nipmucs joined Metacomet's war, known as King Philip's War, in 1675, though they were unable to defeat the colonists. Many Nipmuc were held captive on Deer Island in Boston Harbor and died of disease and malnutrition, while others were executed or sold into slavery in the West Indies.

Christian missionary John Eliot arrived in Boston in 1631. After learning the Massachusett language, which was widely understood throughout New England, he converted numerous Native Americans to Christianity, and with the help of Wawaus, also known as James the Printer (Nipmuc), published a Bible translated in Massachusett and a Massachusett grammar. Backed by the colonial government, he established several "Indian plantations" or praying towns, where Native Americans were induced to settle and be instructed in European customs and converted to Christianity.

The state of Massachusetts has a government-to-government relationship with the Hassanamisco Nipmuc and the Chaubunagungamaug Band of Nipmuc Indians.

The tribe is first mentioned in a 1631 letter by Deputy Governor Thomas Dudley as the Nipnet, 'people of the freshwater pond', due to their inland location. This derives from Nippenet and includes variants such as Neipnett, Neepnet, Nepmet, Nibenet, Nopnat and Nipneet. In 1637, Roger Williams recorded the tribe as the Neepmuck, which derives from Nipamaug, 'people of the freshwater fishing place,' and also appears spelled as Neetmock, Notmook, Nippimook, Nipmaug, Nipmoog, Neepemut, Nepmet, Nepmock, Neepmuk, Nepmug, as well as modern Nipmuc(k). Colonists and the Native Americans themselves used this term extensively after the growth of the praying towns. The French referred to most New England Native Americans as Loup, meaning 'Wolf [people]'. But Nipmuc refugees who had fled to French Colonial Canada and settled among the Abenaki referred to themselves as ȣmiskanȣakȣiak, meaning the 'beaver tail-hill people'.

The Nipmuc most likely spoke Loup A, a Southern New England Algonquian language. The language is undergoing revival within the communities. There are several second-language speakers.

Daniel Gookin (1612–1687), Superintendent to the Native Americans and assistant of Eliot, was careful to distinguish the Nipmuc (proper), Wabquasset, Quaboag, and Nashaway tribes. The situation was fluid since these Native groups were decentralized, and individuals unhappy with their chiefs freely joined other groups. In addition, shifting alliances were made based on kinship, military, and tributary relationships with other tribes.

The formation of the praying towns dissolved some tribal divisions, as members of different tribes settled together. Four groups that are associated with the Nipmuc peoples survive today.