Proceedings of the Harvard Celtic Colloquium, Volume 43 showcases the wide geographic, temporal, and linguistic range of the presentations at the 2024 Harvard Celtic Colloquium. This volume contains Liam Breatnach’s 2024 J. V. Kelleher lecture on the Senchas Már, an early Irish legal text and Benjamin Bruch’s keynote address on the quantity system shared by the p-Celtic languages Cornish and Welsh. The ten other articles present detailed studies of various aspects of Irish and Welsh language, literature, folklore, and culture, both medieval and contemporary. Several of them examine Irish and Welsh literature in a European context. These range from analysis of portrayal of Ireland in film, to enduring lore concerning the Irish famine, to themes of ecology in the writing of Rachel Carson and R. Williams Parry. Two articles examine religious tenets, one on the medieval context of the Apostles Creed in post Conquest Wales, and the other compares how gender influenced the idea of penance in medieval Ireland and Korea.