A first day cover (FDC) is a cover, envelope, or postcard that is franked by the issuing country or territory on the first day of a postal stamp’s authorized issue.

These covers, envelopes, and postcards range from plain to elaborate. Many are developed by manufacturers who specialize in producing first day philatelic covers. Covers get sent in advance to the post office or event authorized to release the stamp first.   

Before the official first day of issue ceremonies, post offices issued stamps as soon as they received them. Extensive research is necessary to establish the first day of sale for early stamps.

The manufacture of special first day covers with cachets (an informative illustration using on the left-hand side of an envelope or postcard providing information about the theme of the stamp) began in the late 1920s and experienced a Golden Age in the 1950s through 1980s.

In the United States, George Linn is credited with creating the first text cachet in 1926. Freelance illustrators such as Charles Chickering, who previously designed stamps, have created artwork for many first day covers.

The United States Postal Service selects a location or several locations that are designated “official” first day cities. It also prepares unique first day covers that are sold in competition with handcrafted or commercial printed products.