Wireless Telegraphy is electronic signalling, through the ground, bodies of water, or the air, which does not require the direct metallic connection, from transmitter to receiver, that was needed by the original electric telegraphs. The term covers a number of related technologies developed beginning in the mid-1800s, including earth conduction, electrostatic induction, electromagnetic induction, and, most importantly, electromagnetic radiation (radio).

Radio proved to be by far the most efficient of these methods, so, beginning around 1900, most references to "wireless" actually refer to radio transmissions, and for those purposes "wireless telegraph" was eventually supplanted by the more precise term "radiotelegraph". But, with the eventual near-disappearance of telegraphic signalling, even this latter term is now very rarely used, although text messaging by mobile telephone could be considered a form of radiotelegraphy.