The Penny Black was the world's first adhesive postage stamp used in a public postal system. It was first issued in Great Britain on 1 May 1840, but was not valid for use until 6 May. It features a profile of Queen Victoria.
In 1837, British postal rates were high, complex and anomalous. To simplify matters, Sir Rowland Hill proposed an adhesive stamp to indicate pre-payment of postage. At the time it was normal for the recipient to pay postage on delivery, charged by the sheet and on distance travelled. By contrast, the Penny Black allowed letters of up to 1/2 ounce (14 grams) to be delivered at a flat rate of one penny, regardless of distance.
Postal delivery systems using what may have been adhesive stamps existed before the Penny Black. The idea had at least been suggested earlier in the Austrian Empire, Sweden, and possibly Greece.
On 13 February 1837, Sir Rowland Hill proposed to a government enquiry both the idea of a pre-paid stamp and a pre-paid envelope, a separate sheet folded to form an enclosure for carrying letters. Hill was given a two-year contract to run the new system, and together with Henry Cole he announced a competition to design the new stamps. There were some 2,600 entries, but none was considered suitable; instead a rough design endorsed by Hill was chosen, featuring an easily recognisable profile of the former Princess Victoria. Hill believed this would be difficult to forge. An envelope bearing a reproduction of a design created by the artist William Mulready was also issued.