Great Bay (New Hampshire)

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.

Tributaries to Great Bay include the Bellamy River, the Oyster River, the Lamprey River, the Squamscott River, and the Winnicut River. The bay is home to the Great Bay National Estuarine Research Reserve and the Great Bay National Wildlife Refuge.