For a few years, the 'world's shortest river' was only 61 metres long

In 1989, Guinness World Records named Montana's Roe River, a stream flowing just 61 metres from a natural spring into the Missouri River, the world's shortest. The title was disputed by Oregon's D River and others with similarly tiny lengths, and Guinness eventually retired the category rather than settle the argument.

— Wikipedia contributors, Roe River — Montana, USA