- Y BARDD COCH O FÔN - see HUGHES, HUGH
- Y BRAWD - see MADOG ap GWALLTER
- YALE family Plâs yn Iâl, Plas Grono,
- YALE, DAVID (d. 1626), chancellor of Chester - see YALE
- YALE, ELIHU (1649 - 1721), India merchant - see YALE
- YALE, THOMAS (c. 1526 - 1577), ecclesiastical lawyer - see YALE
- YARDLEY, EDWARD (1698 - 1769), archdeacon
- YATES, WILFRID NIGEL (1944 - 2009), archivist and historian
- YNYR GWENT - see WATKINS, THOMAS EVAN
- YONG, JOHN - see MORGAN, JOHN
- YORKE, PHILIP (1743 - 1804) Erddig, Erthig,, antiquary
- YORKE, PHILIP SCOTT (1905 - 1976), Squire of Erddig, near Wrexham
- YORKE, SIMON (1903 - 1966), nobleman and soldier
- YOUNG, DAVID (1844 - 1913), Wesleyan minister and historian
- YOUNG, GRUFFYDD (c. 1370 - c. 1435), cleric, and supporter of Owain Glyndŵr
- YOUNG, JAMES JUBILEE (1887 - 1962), Baptist minister
- YOUNG, JOHN - see MORGAN, JOHN
- YOUNG, THOMAS (1507 - 1568), archbishop of York
- YR ARIAN MAWR - see HUGHES, OWEN
- YR ESTYN - see LLOYD, THOMAS RICHARD
- YR HEN FICER - see PRICHARD, RHYS
- YSGAFELL - see WILLIAMS, JANE
- YSTRWYTH (fl. 1204-1222), cleric - see IORWERTH ap MADOG
- YSTUMLLYN, JOHN (d. 1786), gardener and land steward
- YWAIN MEIRION - see GRIFFITH, OWEN