A flatboat was a rectangular flat-bottomed boat with square ends used to transport freight and passengers on inland waterways in the United States. The flatboat could be any size, but essentially it was a large, sturdy tub with a hull.

A keelboat is a riverine cargo-capable working boat, or a small- to mid-sized recreational sailing yacht. The boats in the first category have shallow structural keels, and are nearly flat-bottomed and often used leeboards if forced in open water, while modern recreational keelboats have prominent fixed fin keels, and considerable draft. The two terms may draw from cognate words with different final meaning.