The Pocumtuc (v. Pocomtuck) or Deerfield Indians were a prominent Native American tribe originally inhabiting western areas of what is now Massachusetts, especially around the confluence of the Deerfield and Connecticut Rivers in today's Franklin County. Their territory also included much of current-day Hampden and Hampshire Counties, plus areas now in northern Connecticut and southern Vermont. Their principal village, also known as Pocumtuck, was in the vicinity of the present day village of Deerfield. Their language, now extinct, was an R-dialect of the Algonquian language family, most likely related to the Wappinger and nearby Mahican tribes of the Hudson River Valley.
Little is known about the Pocumtuck people, but it is believed they led a lifestyle similar to other tribes of New England. They would have engaged in semi-sedentary agriculture of maize, beans, and squash. They also hunted game and fished in the Connecticut River, which served as a major inland transportation route. The Pocumtuck were decimated by intertribal warfare with the powerful Mohawk, then based in present-day New York, and by smallpox epidemics after European contact. They had no immunity to the new disease and suffered high fatalities. In addition, they lost tribal members due to taking part in wars among the Dutch, English, French, and their respective Native American allies.