Cousins River

{{Use American English|date=February 2025}}

{{Infobox river

| name = Cousins River

| image =Cousins River.jpg

| image_size =

| image_caption =The river below Granite Street in Yarmouth, near its confluence with the Royal River

| source1_location = Maine

| mouth_location =

| subdivision_type1 = Country

| subdivision_name1 = United States

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|name_other=Sisquisic (Native American)}}

The Cousins River (Native American: Sisquisic){{Cite book |title=Collections of the Maine Historical Society: Volume 2 |publisher=Maine Historical Society |year=1847 |pages=167}} is a {{convert|4.7|mi|km|adj=mid|-long}}, primarily tidal river in southern Maine. Rising in the town of Freeport at the junction of Harvey Brook and Merrill Brook, it flows south and forms, for most of its course, the boundary between Freeport and Yarmouth. It flows into the Royal River just west of its mouth in Casco Bay.

The river, Cousins Island and Littlejohn Island are named after Englishman John Cousins ({{circa|1596}}–1682), who emigrated from Marlborough, Wiltshire.