What Native American tribe was at the first Thanksgiving feast?

The Wampanoag was a loose knit collection of many sub-tribes including the Patuxet. In 1620 the Mayflower ship arrived at New Plymouth and established a colony. The first year was difficult with half of the pilgrims dying.

The first Thanksgiving was held in the fall of 1621 and was actually a Harvest Feast. Squanto a native of the Patuxet people was at the feast and stayed on with the colony to help them survive and adapt in the new world. Squanto had been taken to Europe by earlier explorers and he had learned to speak English. The Pilgrim colony was established on an old Patuxet village site that had been abandoned due to death of the tribe by disease.

Wampanoag translates to "People of the Dawn" and descendants of this tribe still exist in East Coast states.