Daughter of Llŷr and Penarddun; given in marriage to Matholwch king of Ireland as the foundation-alliance between the Welsh and Irish polities; mother of Gwern. The eponymous figure of the Mabinogi Second Branch (Branwen ferch Llŷr). The starling-message episode — Branwen training a starling to carry a message of her abuse at Matholwch's court across the Irish Sea to her brother Bendigeidfran in Britain — is one of the most-poignant tableaux of medieval Welsh literature, structurally central to the Branch-2 narrative pivot from peace-and-marriage to war-and-destruction. After the catastrophic Welsh-Irish war that her message precipitated, in which both her son Gwern (thrown into a fire by Efnisien) and her brother Bendigeidfran (mortally wounded) were killed, Branwen returned to Britain with the seven survivors and died of grief at Aber Alaw, declaring "Alas, two good islands have been laid waste because of me." Buried at the Bedd Branwen Bronze-Age cairn on the Llanddeusant peninsula of Anglesey — one of the most-famous toponymic-archaeological anchors of Welsh medieval tradition.