According to Montana Kids, the shortest river in the world is Roe River, as verified by the Guinness Book of World Records. The Roe River is in Montana, and it is 200 feet long.
It runs between the Missouri River and Giant Springs, a large freshwater spring. The D River in Oregon was originally awarded the title of being the shortest river in the world, in 1940, with accounts showing it to be 440 feet long and running from Devils Lake to the Pacific Ocean. However, in 1987 it was discovered that the Roe River measured just 201 feet long, being about half the size of the D River. The D River actually only reaches a length of 440 feet twice a year, with a length of just 120 feet during the spring tide. For this reason, the debate as to which river is officially the shortest is still in contention.