The article is an interdisciplinary study, aiming to portray the historical geography and toponymy of the Thái Bình estuary, thereby expanding observations to reconstruct its 1,000-year history. Research results show that the Thái Bình estuary had the ancient name of Đại Bàng estuary. Since the 10th century, the estuary has been part of an important chain of estuaries ruled by coastal chiefs such as Trần Lãm and Đinh Bộ Lĩnh. During the 16th and 17th centuries, when the mainstream of the Red River moved southwards, the Thái Bình River became the most important one for the region, especially with the route along Domea, Phố Hiến, and Thăng Long. At the end of the 19th century, when Hải Phòng was becoming an important seaport, the Thái Bình estuary played a minor role in water transport.