Holy cards are small, mass-produced, devotional pictures made for the use of the Roman Catholic faithful. They typically depict a religious scene or a saint on a small image that is about the size of a playing card or collectable card. The reverse typically contains a prayer, some of which promise an indulgence for its recitation. The circulation of these cards is an important part of the visual folk culture of Roman Catholics.

Early holy cards were often woodcuts; the first surviving example is from 1423, and depicts Saint Christopher. The visual crudity of the images possible in this medium was alleviated somewhat by the elaborate paper lace that surrounded the images; these images were called dévotes dentelles in France and Andachtsbilder in Germany, the two chief early centres for their manufacture and circulation.

The invention of lithography made it possible to reproduce images of greater sophistication, leading to a much broader circulation of the cards. An early centre of their manufacture was in the environs of the Church of St Sulpice in Paris; the lithographed images made there were done in delicate pastel colours, and proved extremely influential on later designs. Belgium and Germany also became centres of the manufacture of holy cards, as did Italy in the twentieth century.

St. Catherine, a colored lithograph

Special holy cards are printed by Roman Catholics to be distributed at funerals; these are "memorial cards", with details of the person whom they commemorate as well as prayers printed on the back. Other specialized holy cards remember baptisms, confirmations, and other religious anniversaries. Others are not customized, and circulate to promote the veneration of the saints and images they bear.

At the end of the nineteenth century, some Protestant denominations attempted to answer these Roman Catholic images with similar images of their own. They produced "Bible cards" or "Sunday school cards", with lithographed illustrations depicting Biblical stories and parables, more modern scenes of religious life or prayer, or sometimes just a Biblical text illuminated by calligraphy; these were linked to Biblical passages that related to the image. The reverse typically held a brief sermon instead of a prayer. Imagery here was always the servant of text, and as such these Protestant cards tended to be replaced by tracts that emphasized message instead of imagery, and were illustrated with cartoon-like images if they were illustrated at all.