Weir River is a short stream and estuary that empties into Hingham Bay, part of Boston Harbor in Massachusetts, United States.

[2][3] Weir River is formed at the confluence of Crooked Meadow River and Fulling Mill Brook in Hingham near the intersection of Free Street and Massachusetts Route 228 which are fed by Cushing Pond, Fulling Mill Pond, and the wetlands around Jacob's Meadow.

On the west side of Weir River estuary lies World's End, another Trustees of Reservations park.

The estuary reaches Hingham Bay at the north side of the World's End peninsula.

[5] In 2005, the Commonwealth of Massachusetts designated the Weir River Watershed as "high stressed",[6] meaning the rate of dewatering, from seasonal low precipitation and water supply withdrawals, exceeds the rate of recharge, from natural rainfall, for extended periods during the year.