The Series of 1902, also known as the Second Bureau Issue, is a set of definitive postage stamps in fourteen denominations ranging between one cent and five dollars, produced by the U. S. Bureau of Engraving and Printing and issued by the United States Post Office. Two denominations appeared in November and December 1902 and the other twelve were released between January and June 1903. These stamps were assigned the Scott Catalogue numbers 300 through 313. Also considered part of the series is a fifteenth stamp which appeared in November 1903—a second version of the 2¢ value, the original having faced severe criticism. This series, particularly noted for its exceptional ornateness and opulence of design, remained in circulation until late 1908, when it was superseded by the Washington-Franklin Issues.

A definitive stamp is a postage stamp that is part of the regular issue of a country's stamps, available for sale by the post office for an extended period of time and designed to serve the everyday postal needs of the country. The term is used in contrast to a "provisional stamp", one that is issued for a temporary period until regular stamps are available, or a "commemorative stamp", a stamp "issued to honor a person or mark a special event" available only for a limited time. Commonly, a definitive issue or series includes stamps in a range of denominations sufficient to cover current postal rates. An "issue" generally means a set that is put on sale all at the same time, while a "series" is spread out over several years, but the terms are not precise. Additional stamps in a series may be produced as needed by changes in postal rates; nevertheless some values may be permanently available, regardless of prevailing rates; examples include 1c or 1p and $1 or £1.