Owen Ultach (; died 26 October 1586) was a sixteenth-century Irish physician. He was the ollam leighis (official physician) to the OâÂÂDonnell clan of Tyrconnell.
Ultach was born in the sixteenth century to the àDuinnshléibhe family. Formerly the ruling dynasty of Ulaid, by the late-fourteenth century, they were a medical family of physicians to the O'Donnell clan. Certain family members went by the alternate surname Ultach, after Ulaid.
His father Donnchadh was the ollam leighis before him. Ultach may have been named after his paternal grandfather, Owen.
Ultach was, like his father, educated in the medical arts in Paris and known for his general learning. He was considered the finest physician of his time in Ireland.
Owen Ultach died on 26 October, 1586. His obituaries in the Annals of the Four Masters and the Annals of Ulster read, respectively:
Ultach is the last recorded ollam leighis to the O'Donnell clan. By the early 1600s, Tyrconnell-born Niall àGlacáin was working as a physician to the clan.