A relay league is a chain of message forwarding stations in a system of optical telegraphs, radio telegraph stations, or riding couriers.

An interesting description of these early 19th century methods and its evolution into the electric telegraph networks of the mid and late 1800's is found in "The Victorian Internet", a book by Tom Standage ISBN 0-425-18169-8 .

Radio amateurs have been early in arranging relay leagues, as is reflected in the name of the organization of American Radio Relay League (ARRL), http://www.arrl.org/

Radio amateur message relay operations were originally conducted using Morse Code in the first two decades of the 20th century using spark transmitters. As vacuum tubes became affordable operations shifted to more efficient manual telegraphy transmitters, referred to as CW (Continuous Wave). Messages were relayed station to station typically covering four or more re-transmission cycles to cover the continental US, in an organized system of amateur radio networks. After World War II, voice and radio-teletype implementations of the message relay system were employed.