The Book of Leinster ( , LL) is a medieval Irish manuscript compiled 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.

Date and provenance

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.

Best's suggestion is corroborated by evidence from Dublin, Royal Irish Academy MS B. iv. 2, also of the early 17th century. As Rudolf Thurneysen noted, the scribe copied several texts from the Book of Leinster, identifying his source as the "Leabhar na h-Uachongbála", presumably for Leabhar na Nuachongbála ("Book of Noughaval"). Third, in the 14th century, the Book of Leinster was located at Stradbally (County Laois), the place of a monastery known originally as Nuachongbáil "of the new settlement" (Noughaval) and later as Oughaval.<!-- Still need to read the article -->

Contents

The manuscript has 187 leaves, each approximately . A note in the manuscript suggests as many as 45 leaves have been lost. The book, a wide-ranging compilation, is one of the most important sources of medieval Irish literature, genealogy and mythology, containing, among many others, texts such as Lebor Gabála Érenn (the Book of Invasions), the most complete version of Táin Bó Cuailnge (the Cattle Raid of Cooley), the Metrical Dindshenchas and an Irish translation/adaptation of the De excidio Troiae Historia, and before its separation from the main volume, the Martyrology of Tallaght.

A diplomatic edition was published by the Dublin Institute for Advanced Studies in six volumes over a period of 29 years.

Conservation and display

Following two years of extensive conservation, the Book of Leinster will be on display at Trinity College Dublin until August 2025.