Great Marsh
{{Infobox body of water
| name = Great Marsh
| native_name =
| native_name_lang =
| other_name = Great Salt Marsh
| image = Aerial View of Great Marsh in Massachusetts.jpg
| alt = The Great Marsh in Plum Island, Newbury, and Ipswich, Massachusetts
| caption = The Great Marsh in Plum Island, Newbury, Rowley, and Ipswich, Massachusetts
| image_bathymetry =
| alt_bathymetry =
| caption_bathymetry =
| location = {{flag|Massachusetts}}
{{flag|New Hampshire}}
| group =
| coordinates = {{coord|42.735277|-70.818914|region:ZZ_type:waterbody|display =inline,title}}
| type = Saltmarsh
| etymology =
| part_of =
| inflow =
| rivers = Parker River
| outflow =
| oceans = Atlantic Ocean
| catchment =
| basin_countries =
| agency =
| designation =
| date-built =
| engineer =
| date-flooded =
| length =
| width =
| area = {{convert|20,000|-|30,000|acre}}
| depth =
| max-depth =
| volume =
| residence_time =
| salinity = Salt Water
| shore =
| elevation =
| temperature_high =
| temperature_low =
| frozen = Salt water Lake
| islands = Plum Island
| islands_category = Barrier islands
| sections =
| trenches =
| benches =
| cities =; In New Hampshire:
; In Massachusetts:
| pushpin_map = Massachusetts
| pushpin_label_position =
| pushpin_map_alt =
| pushpin_map_caption =
| website =
| reference =
}}
The Great Marsh (also sometimes called the Great Salt Marsh{{cite web |title=Great Salt Marsh |url=http://datazone.birdlife.org/site/factsheet/great-salt-marsh-iba-usa/details |website=BirdLife International |accessdate=5 June 2018}}) is a long, continuous saltmarsh in eastern New England extending from Cape Ann in northeastern Massachusetts to the southeastern coast of New Hampshire.{{cite web |title=The Great Marsh |url=http://www.greatmarsh.org/ |website=Great Marsh Coalition |publisher=Great Marsh Coalition |accessdate=5 June 2018}} It includes roughly 20,000–30,000{{cite web |title=Great Marsh ACEC |url=https://www.mass.gov/service-details/great-marsh-acec |website=Mass.gov |publisher=Commonwealth of Massachusetts |accessdate=5 June 2018}}{{cite web |title=Site Summary: Great Marsh |url=https://www.massaudubon.org/our-conservation-work/wildlife-research-conservation/statewide-bird-monitoring/massachusetts-important-bird-areas-iba/important-bird-area-sites/great-marsh |website=Mass Audubon |publisher=Massachusetts Audubon Society |accessdate=5 June 2018}} acres of saltwater marsh, mudflats, islands, sandy beaches, dunes, rivers, and other water bodies. The Great Marsh comprises much of the northeastern half of Essex County, Massachusetts, and touches the towns and cities of Gloucester, Essex, Ipswich, Rowley, Newbury, Newburyport, and Salisbury in Massachusetts as well as the towns of Seabrook and Hampton in New Hampshire.{{cite web |title=Great Marsh Coastal Adaptation Plan |url=https://www.nwf.org/greatmarshadaptation |website=The National Wildlife Federation |publisher=The National Wildlife Federation |accessdate=5 June 2018}}{{cite web |title=Hampton Brochure |url=http://www.nhaudubon.org/wp-content/uploads/2014/10/Hampton-Brochure-final-web.pdf |website=NH Audubon |publisher=New Hampshire Audubon Society |accessdate=5 June 2018}} It is a designated Important Bird Area.