Book of Leinster

The Book of Leinster (Middle Irish: Lebor Laignech pronounced [ˈl̠ʲeβəɾ ˈl̪aɣʲnʲəx], LL) is a medieval Irish manuscript compiled c. 1160 and now kept in Trinity College Dublin. It was formerly known as the Lebor na Nuachongbála ("Book of Nuachongbáil"), a monastic site known today as Oughaval.

In 2023, Trinity College started an extensive restoration project to make the manuscript available for public viewing.

Fragments of the book, such as the Martyrology of Tallaght, are in the collection of University College Dublin.^{[citation needed]}

The manuscript is a composite work and more than one hand appears to have been responsible for its production. The principal compiler and scribe was probably Áed Ua Crimthainn, who was abbot of the monastery of Tír-Dá-Glas on the Shannon, now Terryglass (County Tipperary), and the last abbot of that house for whom we have any record. Internal evidence from the manuscript itself bears witness to Áed's involvement. His signature can be read on f. 32r (p. 313): Aed mac meic Crimthaind ro scrib in leborso 7 ra thinoil a llebraib imdaib ("Áed Húa Crimthaind wrote this book and collected it from many books"). In a letter copied by a later hand into a bottom margin (p. 288), the bishop of Kildare, Finn mac Gormáin (d. 1160), addresses him as a man of learning (fer léiginn) of the high-king of Leth Moga, the coarb (comarbu lit. 'successor') of Colum mac Crimthainn, and the chief scholar (prímsenchaid) of Leinster. An alternative theory was that by Eugene O'Curry, who suggested that Finn mac Gormáin transcribed or compiled the Book of Leinster for Áed.

The manuscript was produced by Aéd and some of his pupils over a long period between 1151 and 1224. From annals recorded in the manuscript we can say it was written between 1151 and 1201, with the bulk of the work probably completed in the 1160s. As Terryglass was burnt down in 1164, the manuscript must have been finalised in another scriptorium. Suggested locations include Stradbally (Co. Laois) and Clonenagh (County Laois), the home of Uí Chrimthainn (see below).

Eugene O'Curry suggested that the manuscript may have been commissioned by Diarmait Mac Murchada (d. 1171), king of Leinster, who had a stronghold (dún) in Dún Másc, near Oughaval (An Nuachongbáil). Dún Másc passed from Diarmait Mac Murchada to Strongbow, from Strongbow to his daughter Isabel, from Isabel to the Marshal Earls of Pembroke and from there, down several generations through their line. When Meiler fitz Henry established an Augustinian priory in County Laois, Oughaval was included in the lands granted to the priory.^{[citation needed]}

Nothing certain is known of the manuscript's whereabouts in the next century or so after its completion, but in the 14th century, it came to light at Oughaval. It may have been kept in the vicarage in the intervening years.^{[citation needed]}

The Book of Leinster owes its present name to John O'Donovan (d. 1861), who coined it on account of the strong associations of its textual contents with the province of Leinster, and to Robert Atkinson, who adopted it when he published the lithographic facsimile edition.