Plymouth Colony was an English colonial venture in North America from 1620 until 1691. The first settlement was at New Plymouth, a location previously surveyed and named by Captain John Smith. The settlement, which served as the capital of the colony, is today the modern town of Plymouth, Massachusetts. At its height, Plymouth Colony occupied most of the southeastern portion of the modern state of Massachusetts.

Founded by a group of separatists who later came to be known as the Pilgrims, Plymouth Colony was, along with Jamestown, Virginia, one of the earliest colonies to be founded by the English in North America and the first sizable permanent English settlement in the New England region. Aided by Squanto, a Native American, the colony was able to establish a treaty with Chief Massasoit which helped to ensure the colony's success. The colony played a central role in King Philip's War, one of the earliest and bloodiest of the Indian Wars. Ultimately, the colony was annexed by the Massachusetts Bay Colony in 1691.

Plymouth holds a special role in American history. Rather than being entrepreneurs like many of the settlers of Jamestown, the citizens of Plymouth were fleeing religious persecution and searching for a place to worship God as they saw fit. The social and legal systems of the colony were thus closely tied to their religious beliefs. Many of the people and events surrounding Plymouth Colony have become part of American mythology, including the North American tradition known as Thanksgiving and the monument known as Plymouth Rock. Despite the colony's relatively short history, it has become an important symbol of what is now labeled "American", owing largely to its treatment in American public schools.