Great Bay is a tidal estuary located in Strafford and Rockingham counties in eastern New Hampshire, United States. The bay occupies over 6,000 acres (24 km2), not including its several tidal river tributaries. Its outlet is at Hilton Point in Dover, New Hampshire, where waters from the bay flow into the Piscataqua River, thence proceeding southeast to the Atlantic Ocean near Portsmouth. The northern end of the bay, near its outlet, is referred to as Little Bay.

Dover is a city in Strafford County, New Hampshire, United States. The population was 32,741 at the 2020 census, making it the most populous city in the New Hampshire Seacoast region and the 5th most populous city in New Hampshire.