The Keystone Pipeline System is an oil pipeline system in Canada and the United States. It runs from the Western Canadian Sedimentary Basin in Alberta, Canada, to refineries in the United States in Steele City, Nebraska; Wood River and Patoka, Illinois; and the Gulf Coast of Texas.

The Keystone XL pipeline (Phase IV) is a proposed route, similar to the Phase I pipeline – between Hardisty, Alberta, and Steele City, Nebraska – but shorter and with a larger-diameter pipe. It would run through Baker, Montana, where American-produced light crude oil from the Williston Basin (Bakken formation) of Montana and North Dakota would be added to the Keystone's current throughput of synthetic crude oil (syncrude) and diluted bitumen (dilbit) from the oil sands of Canada. However, after more than six years of review, the United States President Barack Obama announced on November 6, 2015, his administration's rejection of the fourth phase. More: