Electrical telegraphy is point-to-point distance communicating via sending electric signals over wire, a system primarily used from the 1840s until the late 20th century. It was the first electrical telecommunications system and the most widely used of a number of early messaging systems called telegraphs, that were devised to send text messages more quickly than physically carrying them. Electrical telegraphy can be considered the first example of electrical engineering.

Electrical telegraphy consisted of two or more geographically separated stations, called telegraph offices. The offices were connected by wires, usually supported overhead on utility poles. Many electrical telegraph systems were invented that operated in different ways, but the ones that became widespread fit into two broad categories. First are the needle telegraphs, in which electric current sent down the telegraph line produces an electromagnetic force that moves a needle-shaped pointer into position over a printed list, in order to point to a specific item in that list (such as a letter of the alphabet). Early needle telegraph models used multiple needles, thus requiring multiple wires to be installed between stations. The first commercial needle telegraph system and the most widely used of its type was the Cooke and Wheatstone telegraph, invented in 1837. The second category are armature systems, in which the current activates a telegraph sounder that makes a click; communication on this type of system relies on sending clicks in coded rhythmic patterns. The archetype of this category was the Morse system and the code associated with it, both invented by Samuel Morse in 1838. In 1865, the Morse system became the standard for international communication, using a modified form of Morse's code that had been developed for German railways.

Electrical telegraphs were used by the emerging railway companies to provide signals for train control systems, minimizing the chances of trains colliding with each other. This was built around the signalling block system in which signal boxes along the line communicate with neighbouring boxes by telegraphic sounding of single-stroke bells and three-position needle telegraph instruments.

In the 1840s, the electrical telegraph superseded optical telegraph systems such as semaphores, becoming the standard way to send urgent messages. By the latter half of the century, most developed nations had commercial telegraph networks with local telegraph offices in most cities and towns, allowing the public to send messages (called telegrams) addressed to any person in the country, for a fee.

Beginning in 1850, submarine telegraph cables allowed for the first rapid communication between people on different continents. The telegraph's nearly-instant transmission of messages across continents – and between continents – had widespread social and economic impacts. The electric telegraph led to Guglielmo Marconi's invention of wireless telegraphy, the first means of radiowave telecommunication, which he began in 1894.

In the early 20th century, manual operation of telegraph machines was slowly replaced by teleprinter networks. Increasing use of the telephone pushed telegraphy into only a few specialist uses; its use by the general public dwindled to greetings for special occasions. The rise of the Internet and email in the 1990s largely made dedicated telegraphy networks obsolete.

From early studies of electricity, electrical phenomena were known to travel with great speed, and many experimenters worked on the application of electricity to communications at a distance. All the known effects of electricity – such as sparks, electrostatic attraction, chemical changes, electric shocks, and later electromagnetism – were applied to the problems of detecting controlled transmissions of electricity at various distances.

In 1753, an anonymous writer in the Scots Magazine suggested an electrostatic telegraph. Using one wire for each letter of the alphabet, a message could be transmitted by connecting the wire terminals in turn to an electrostatic machine, and observing the deflection of pith balls at the far end. The writer has never been positively identified, but the letter was signed C.M. and posted from Renfrew leading to a Charles Marshall of Renfrew being suggested. Telegraphs employing electrostatic attraction were the basis of early experiments in electrical telegraphy in Europe, but were abandoned as being impractical and were never developed into a useful communication system.