St. Croix is a rural community in York County, New Brunswick, Canada.
The community derives its name from the St. Croix River which flows along its western boundary; this river also forms the Canada–United States border and the community is opposite Vanceboro, Maine to the west.
St. Croix is located 8 kilometres west of the village of McAdam. The western terminus of Highway 4 is at the border on the Saint Croix-Vanceboro Bridge over the St. Croix River, where it connects with the eastern terminus of Highway 6 in Maine. The New Brunswick Southern Railway crosses the river using the Saint Croix-Vanceboro Railway Bridge.
The Canada Border Services Agency maintains a customs station in St. Croix immediately east of the bridge.
During the 1800s, St. Croix developed as an isolated lumbering settlement, however in the 1860s the community was selected for the crossing point for the European & North American Railway (Western Extension) which was constructing a line from Saint John to Vanceboro. At Vanceboro, a sister company's line had opened through to Bangor in 1869. An iron railway bridge on stone piers was constructed over the St. Croix, measuring approximately 30 metres (100 feet) in length. The opening ceremony in 1871 of the railway line between the two countries was attended by Governor General of Canada Lord Lisgar and President of the United States Ulysses S. Grant.