Tidnish River

Infobox River
river_name = Tidnish River

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caption = Tidnish River near arch bridge for the defunct Chignecto Ship Railway.
origin =
mouth = Northumberland Strait
basin_countries = Canada
length =
elevation =
mouth_elevation = sea level
discharge =
watershed =

The Tidnish River is a short Canadian river on the Isthmus of Chignecto along the interprovincial boundary with New Brunswick and Nova Scotia.

Rising in the northwest corner of Cumberland County, east of the interprovincial boundary, the river's largest tributaries are the West Branch Tidnish River, Little West Branch Tidneish River, Paradise Brook and Chapman's Brook.

The river becomes a tidal estuary at the community of Tidnish Bridge where the Chignecto Ship Railway constructed a large stone masonry bridge across it. At Tidnish Bridge, the river flows the final 2 kilometres in a serpentine manner to discharge into the Northumberland Strait at Jackson's Point on Baie Verte.

This section of the river downstream from Tidnish Bridge also forms part of the interprovincial boundary with New Brunswick.