The Penny Post is any one of several postal systems in which normal letters could be sent for one penny. Five such schemes existed in the United Kingdom while the United States initiated at least three such simple fixed rate postal arrangements.

The London Penny Post was a premier postal system whose function was to deliver mail within London and its immediate suburbs for the modest sum of one penny. The Penny Post was established in 1680 by William Dockwra and his business partner, Robert Murray. Dockwra was a merchant and a member of the Armourer and Brasiers Livery Company and was appointed a Customs Under-Searcher for the Port of London in 1663. Murray would later become clerk in the excise office of the Penny Post. The London Penny Post mail service was launched with weeks of publicity preceding it on 27 March 1680. The new London Penny Post provided the city of London with a much needed intra-city mail delivery system. The new Penny Post was influential in establishing a model system and pattern for the various Provincial English Penny Posts in the years that followed. It was the first postal system to use hand-stamps to postmark the mail to indicate the place and time of the mailing and that its postage had been prepaid. The success of the Penny Post would also threaten the interests of the Duke of York who profited directly from the existing general post office. It also compromised the business interests of porters and private couriers. The Penny Post was also involved in publishing various criticisms towards the British monarchy, the Duke of York in particular, which ultimately led to the takeover of the Penny Post by crown authorities. The earliest known Penny Post postmark is dated 13 December 1680 and is considered by some to be the world's first postage 'stamp'.