D.

D. or d. may refer to, usually as an abbreviation:
 * Don (honorific), a form of address in Spain, Portugal, Italy, and their former overseas empires, usually given to nobles or other individuals of high social rank.
 * Date of death, as an abbreviation.
 * District of Columbia Department of Transportation, whose logo is "d."
 * Schubert Thematic Catalogue, also known as the Deutsch catalogue (or D.), a numbered list of all compositions by Franz Schubert compiled by Otto Erich Deutsch.
 * a penny, from the Latin denarius.