The Pennacook, also known by the names Penacook and Pennacock, were Algonquian Indigenous people who lived in what is now Massachusetts, New Hampshire, and southern Maine.

[2] The Pennacook were related to but not a part of the original Wabanaki Confederacy, which includes the Miꞌkmaq, Maliseet, Passamaquoddy, and Penobscot peoples.

[2] Pennacook was a specific community within this confederacy that also included Accominta,[7] Agawam, Amoskeag, Coosuc, Cowasack, Nashua, Naumkeag, Newickawanoc, Ossipee, Piscataway, Piscatequa, Souhegan, Squamscot, Wambesit, Washacum, Winnepesaukee, Wachusett, and other villages.

David Stewart-Smith (1998:19) estimated that the Merrimack Valley had 8,000–25,000 people before the epidemics, with a median of around 16,500 for the central area around Pennacook.

Many Pennacook villages were built just above natural waterfalls that trapped fish and made it easier to catch them in the late spring.

The presence of southern, fire-resistant species of nut trees like hickories and black walnuts in New Hampshire today is thanks to the Pennacook.

Suffering high mortality, they were in a weakened state and subject to raids by Mohawk of the Iroquois Confederacy from the west, and Micmac (Mi'kmaq) tribes from the north, who also took a toll of lives.

Chief Passaconaway had a military advantage over English colonists from New England, but he decided to make peace with them rather than lose more of his people through warfare.

Although Wonalancet, the chief who succeeded Passaconaway, tried to maintain neutrality in the war, bands of Pennacook in western Massachusetts did not.

The Boy Scouts of America's Boston-based Spirit of Adventure Council adopted the name "Pennacook" for its Order of the Arrow lodge.