The Cathach of St Columba is the oldest extant Irish illuminated manuscript, dating to c. AD 600. The surviving 58 folios contain psalms 30:10 to 105:13. It is understood that Colum Cille copied the manuscript from a psalter lent to him by St Finnian. A dispute over the ownership of the copy was resolved by the King of Tara in a very early copyright ruling in which he stated: ‘To every cow her calf, so to every book its copy’. This full-color 84-page booklet introduces readers to the provenance, art history and biblical content of the manuscript. The accompanying CD-ROM presents the manuscript in digitized form, with a brief overview of its origins and art history. The manuscript folios can be read against a transcription by H.J. Lawlor or an English version of the relevant psalms. High-resolution files allow art historians, calligraphers, palaeographers and other researchers to examine the script and illuminated initials in detail.