| Official Name: | Green Harbor, Massachusetts |
| Settlement Type: | Census-designated place |
| Coordinates: | 42.0742°N -70.6483°W |
| Subdivision Type: | Country |
| Subdivision Type1: | State |
| Subdivision Name1: | Massachusetts |
| Subdivision Type2: | County |
| Subdivision Name2: | Plymouth |
| Subdivision Type3: | Towns |
| Subdivision Name3: | Duxbury Marshfield |
| Area Footnotes: | [1] |
| Area Total Sq Mi: | 0.44 |
| Area Land Sq Mi: | 0.33 |
| Area Water Sq Mi: | 0.11 |
| Area Total Km2: | 1.15 |
| Area Land Km2: | 0.86 |
| Area Water Km2: | 0.28 |
| Population As Of: | 2020 |
| Population Density Km2: | 456.60 |
| Timezone: | Eastern (EST) |
| Utc Offset: | -5 |
| Timezone Dst: | EDT |
| Utc Offset Dst: | -4 |
| Elevation Ft: | 12 |
| Postal Code Type: | ZIP Codes |
| Postal Code: | 02041 (Marshfield) 02332 (Duxbury) |
| Area Code: | 339/781 |
| Blank Name: | FIPS code |
| Blank Info: | 25-27130 |
| Blank1 Name: | GNIS feature ID |
| Blank1 Info: | 2805096 |
| Population Total: | 394 |
| Unit Pref: | Imperial |
| Population Density Sq Mi: | 1183.18 |
Green Harbor is a census-designated place (CDP) in the towns of Marshfield and Duxbury, Plymouth County, Massachusetts, United States. It was first listed as a CDP prior to the 2020 census. At the 2010 census the community was included with neighboring Cedar Crest in a single CDP.
Green Harbor was originally known as "Green's Harbor". The name derives from William Green. The Pilgrim government granted William Green rights to conduct commercial fishing there in about 1627.
Green Harbor Beach has a long wooden board walk upon entering and begins at a jetty to the left and connects to Duxbury Beach farther down on the right. It is mainly occupied by families and young people during the summer months. The Green Harbor parking lot has limited parking spaces restricted to vehicles with a Marshfield beach sticker, which can be purchased for the price of $60 at town hall. There are other local parking lots where visitors are able to purchase a temporary day pass to park, which include the post office and The Lobster Pound. Lifeguards can also be found at this beach in season during the week from 9am until 4:30pm.
Activities specific to this beach area include bridge jumping, boating, and climbing the jetty. The Green Harbor Marina allows people to launch their boats and enjoy a ride right out from the Green Harbor River. There is an annual October Fest on Marginal Street, which features live music, food, shopping stands and entertainment. There are local restaurants nearby, a coffee shop and a general store located on Marginal Street. A seasonal food stand can be found at the entrance of Green Harbor Beach during summer months.