he Randolph Caldecott Medal annually recognizes the preceding year's "most distinguished American picture book for children", beginning with 1937 publications. It is awarded to the illustrator by the Association for Library Service to Children (ALSC), a division of the American Library Association (ALA).  The Caldecott and Newbery Medals are the most prestigious American children's book awards.

The award is named for Randolph Caldecott, a nineteenth-century English illustrator. Rene Paul Chambellan designed the Medal in 1937. The obverse scene is derived from Randolph Caldecott's front cover illustration for The Diverting History of John Gilpin (Routledge, 1878, an edition of the 1782 poem by William Cowper), which depicts Gilpin astride a runaway horse.  The reverse is based on "Four and twenty blackbirds bak'd in a pie", one of Caldecott's illustrations for thenursery rhyme "Sing a Song of Sixpence".

Beside the Caldecott Medal, the committee awards a variable number of citations to worthy runners-up, called the Caldecott Honors or Caldecott Honor Books. Recently there are two to four annual Honors. The Honor Books must be a subset of the runners-up on the final ballot, either the leading runners-up on that ballot or the leaders on one further ballot that excludes the winner.

The artist must be a US citizen or resident and the illustrations must be original to the book, which must be published first or simultaneously in the US in English during the preceding year.

A picture book provides "a visual experience. A picture book has a collective unity of story-line, theme, or concept, developed through the series of pictures" that constitute the book. Picture books for any audience up to age 14 should be considered.

The Medal is "for distinguished illustrations in a picture book and for excellence of pictorial presentation for children". The book must be self-contained, independent of other media for its enjoyment. Components other than illustration should be considered as they bear on effectiveness as a children's picture book.