Packet boats were medium-sized boats designed for domestic mail, passenger, and freight transportation in European countries and in North American rivers and canals, some of them steam driven. They were used extensively during the 18th and 19th centuries and featured regularly scheduled service. Steam driven packets were used extensively in the United States in the 19th century on the Mississippi and Missouri rivers, supplying and bringing personnel to forts and trading posts.

Generally, packet trade is any regularly scheduled cargo, passenger and mail trade conducted by boat or ship. The boats or ships are called "packet boats or packet ships" as their original function was to carry mail.