Groton is a town in northwestern Middlesex County, Massachusetts, United States, within the Greater Boston metropolitan area. The population was 11,315 at the 2020 census. It is home to two prep schools: Lawrence Academy at Groton, founded in 1792 and the third-oldest private school in Massachusetts; and Groton School, founded in 1884.

The town was a battlefield in King Philip's War and Queen Anne's War, as England and France competed through their North American colonies from the 17th century well into the 18th century. It was the birthplace of William Prescott, who commanded the colonial forces at the Battle of Bunker Hill during the American Revolution. In postwar years, it had incidents of insurrection during Shays' Rebellion (1786–1787).

The area surrounding modern-day Groton has, for thousands of years, been the territory of various cultures of indigenous peoples. They settled along the rivers, which they used for domestic tasks, fishing and transportation. Historic tribes were the Algonquian-speaking Nipmuc and Nashaway Indians.

The Anglo-American Groton started with the trading post of John Tinker, who conducted business there with the Nashaway at the confluence of Nod Brook and the Nashua River. The Nashaway called the area Petapawag, meaning "swampy land." As Tinker had, other pioneers followed the Algonquian trails from Massachusetts Bay. They found the region productive for fishing and farming.

The town was officially settled and incorporated in 1655, named for Groton in Suffolk, England. Called The Plantation of Groton, it included all of present-day Groton and Ayer, almost all of Pepperell and Shirley, large parts of Dunstable, Littleton, and Tyngsborough, plus smaller parts of Harvard and Westford in Massachusetts, as well as Nashua and Hollis, New Hampshire.

During King Philip's War, when English colonists and Native Americans tried to destroy each other, on March 13, 1676, Native Americans raided and burned all buildings except for four Groton garrisons. Among those killed was John Nutting, a Selectman at Groton. Survivors fled to Concord and other safe havens. Two years later, many returned to rebuild.

Abenaki warriors attacked the town again during the Raid on Groton in 1694 (during King William's War). Lydia Longley and two of her siblings were taken captive; the rest of their family was killed. Lydia was taken to Montreal where she was ransomed, converted to Catholicism, and joined the Congregation of Notre Dame, a non-cloistered order.

In 1704, during Queen Anne's War, an Abenaki raiding party kidnapped Matthias Farnsworth III from his home and brought him to Montreal.

In June 1707, a French-Abenaki raid captured three children of the large family of Thomas Tarbell and his wife Elizabeth (Wood), cousins to the Longleys. The raiders took them overland and by water to the Mohawk mission village of Kahnawake (also spelled Caughnawaga) south of Montreal. There they could be held for ransom or adopted into the tribe by individual Mohawk families. The trade in captives was carried on for years given the continued warfare between the English and French in Europe and North America.

The two Tarbell boys, John and Zachariah, were adopted by Mohawk families and became fully assimilated. They later each married chiefs' daughters, had families, and became respected chiefs themselves.[10] They were among the founders in the 1750s of Akwesasne, after moving up the St. Lawrence River from Kahnawake to escape the ill effects of traders. The brothers' older sister Sarah Tarbell was ransomed by a French family, and converted to Catholicism. Renamed as Marguerite, she followed Lydia Longley in joining the Congregation of Notre Dame, and served with them for the rest of her life. In the late nineteenth century, a plaque was installed about the Tarbell children at the site of the family's former farm in Groton. Descendants with the Tarbell surname are among the Mohawk living at Kahnewake and Akwesasne in the 21st century.

In 1775, the common in front of the First Parish Church was an assembly area for Minutemen who fought in the Battle of Lexington and Concord.