Mulready stationery describes the postal stationery letter sheets and envelopes that were introduced as part of the British Post Office postal reforms of 1840. They went on sale on 1 May 1840, and were valid for use from 6 May. The Mulready name arises from the fact that William Mulready, a well-known artist of the time, was commissioned to illustrate the part of the letter sheets and envelopes which corresponded with the face area.

A piece of postal stationery is a stationery item, such as a stamped envelope, letter sheet, postal card, lettercard, aerogram or wrapper, with an imprinted stamp or inscription indicating that a specific rate of postage or related service has been prepaid. It does not, however, include any postcard without a pre-printed stamp, and it is different from freepost for preprinted cards issued by businesses. In general, postal stationery is handled similarly to postage stamps; sold from post offices either at the face value of the printed postage or, more likely, with a surcharge to cover the additional cost of the stationery. It can take the form of an official mail issue produced only for the use of government departments.