The Petitcodiac River is a river located in south-eastern New Brunswick, Canada. Local tourist businesses often refer to it as the "chocolate river" due to its distinctive brown mud floor and brown waters. Stretching across a meander length of 79 kilometres, the river traverses Westmorland, Albert, and Kings counties, draining a watershed area of about 2,071 square kilometres (800 sq mi). The watershed features valleys, ridges, and rolling hills, and is home to a diverse population of terrestrial and aquatic species. Ten named tributaries join the river in its course toward its mouth in Shepody Bay. Prior to the construction of a causeway in 1968, the Petitcodiac River had one of the world's largest tidal bores, which ranged from 1 to 2 metres (3.3–6.6 ft) in height and moved at speeds of 5 to 13 kilometres per hour (3.1–8.1 mph). With the opening of the causeway gates in April 2010, the river is flushing itself of ocean silts, and the bore is returning to its former size.

A tidal bore, often simply given as bore in context, is a tidal phenomenon in which the leading edge of the incoming tide forms a wave of water that travels up a river or narrow bay, reversing the direction of the river or bay's current. It is a strong tide that pushes up the river, against the current.