Book of Dimma

The Book of Dimma (Dublin, Trinity College, MS.A.IV.23) is an 8th-century Irish pocket Gospel Book originally from the Abbey of Roscrea, founded by St. Cronan in the County Tipperary, Ireland. In addition to the four Gospels, in between the Gospels of Luke and John, it has an order for the Unction and Communion of the Sick. The surviving illumination of the manuscript is a number of illuminated initials, three Evangelist portrait pages and one page with an Evangelist's symbol.

The gospels other than John are "written for the most part in a rapid cursive script", while John is "by a different scribe, in neat minuscule bookhand". It was signed by its scribe, Dimma MacNathi, at the end of each of the Gospels. This Dimma has been traditionally identified with the Dimma, who was later Bishop of Connor, mentioned by Pope John IV in a letter on Pelagianism in 640. This identification, however, cannot be sustained.

In the 12th century the manuscript was encased in a richly worked cumdach or reliquary case, which remains with it at Trinity. On one face it has panels of openwork decoration in Viking Ringerike style over the wood case. There is a good reproduction of 1908 in the Metropolitan Museum of Art in New York, which is not on display there, but has good illustrations available online, unlike the original piece.