Derbforgaill ingen Maeleachlainn

Dearbhfhorghaill (older spelling: Derbforgaill) (1108–1193), anglicised as Derval, was a daughter of Murchad Ua Maeleachlainn, king of Meath, and of his wife Mor (died 1137), daughter of Muirchertach Ua Briain. She is famously known as the "Helen of Ireland" as her abduction from her husband Tigernán Ua Ruairc by Diarmait Mac Murchada, king of Leinster, in 1152 played some part in bringing the Anglo-Normans to Irish shores, although this is a role that has often been greatly exaggerated and often misinterpreted.

Unusually for a woman of her time, she is mentioned no fewer than five times in contemporary annals: her abduction by Diarmait in 1152 (Annals of Clonmacnoise), (although by the end of the next year she had left Leinster and returned to her family's lands in Meath, possibly after negotiations with her father's family); her donation to the Cistercian abbey of Mellifont of altar cloths, a gold chalice, and 60 ounces of gold during the consecration ceremony in 1157 (Annals of the Four Masters); her completion of the Nuns' Church at Clonmacnoise in 1167 (Annals of the Four Masters); her retirement to Clonmacnoise in 1186 (Annals of Ulster, Annals of Loch Ce); and her death in Clonmacnoise in 1193 (Annals of Ulster, Annals of the Four Masters). As the Annals of Tigernach are attested to being composed contemporary to Dearbhforghaill's time, the fragmentary nature of the older texts is supplanted by newer transcription (as Leinster, Ulster, Connacht, and more fill these gaps.

Tigernán Ua Ruairc had three children, Melaghlin (died 1162), Aed, described as crown prince of Breifne, killed by the Anglo-Normans (died 1171) and Dowchawley (died 1171), wife to Ruaidri Ua Conchobair, high king of Ireland, but whether or not Derbforgaill was their mother is less certain.