Newmarket is a town in Rockingham County, New Hampshire, United States. The population was 8,936 at the 2010 census. Some residents are students and employees at the nearby University of New Hampshire in Durham.

The primary settlement in town, where 5,297 people resided at the 2010 census, is defined as the Newmarket census-designated place, or CDP, and is located at the junction of New Hampshire routes 108 and 152, adjacent to the Lamprey River.

Incorporated in 1727, Newmarket is one of six towns granted by Massachusetts in the last year of the reign of King George I. It started as a parish of Exeter, and was granted full town privileges by the legislature in 1737. It was probably named for Newmarket in Suffolk, England. The Lamprey River, running through the town, was named for John Lamprey, an early settler. For a while, the town was called Lampreyville. Newmarket was a center of the New England shipping trade with the West Indies, including importation of sugar and African slaves.

The Newmarket Manufacturing Company was incorporated in 1822, and constructed its first cotton textile mill during 1823 and 1824. The company dominated the mill town's waterfront and economy with seven textile mills harnessing water power at the falls. The company had cotton shipped up from the Deep South, so its production was adversely affected by the American Civil War. It built numerous support structures, including multi-family housing for workers. The company built dams upriver to create Pawtuckaway Pond in Nottingham and Mendums Pond in Barrington—during drought, the company could release a regulated flow of water from the dams into the Lamprey to run the works. The company closed in 1929.

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