- DIRWYNYDD - see DYKINS, WILLIAM
- DIVERRES, POL (1880 - 1946), linguist, Celtic scholar, and sometime Keeper of manuscripts in the National Library of Wales
- DIWYGIWR, Y - see ROBERTS, EVAN JOHN
- DOCTOR COCH, Y - see PRYS, ELLIS
- DODD, CHARLES HAROLD (1884 - 1973), biblical scholar
- DOFWY - see JONES, RICHARD
- DOGFAEL Saint - see Saint DOGMAEL
- DOGMAEL (fl. 6th century), saint
- DOGWEL Saint - see DOGMAEL, Saint
- DOLBEN family Segrwyd,
- DOLBEN, WILLIAM LLOYD Rhiwedog (fl. 19th century) - see LLOYD
- DON, HENRY - see DWN, HENRY
- DONALDSON, JESSIE (1799 - 1889), teacher and anti-slavery activist
- DONNE, JAMES (1764 - 1844), cleric and schoolmaster
- DONNELLY, DESMOND LOUIS (1920 - 1974), politician and writer
- DOUGLAS-PENNANT, Penrhyn - see PENNANT
- DOULBEN, Segrwyd - see DOLBEN
- DOULBIN, Segrwyd - see DOLBEN
- DOWNMAN, JOHN (1749 - 1824), painter
- DRISCOLL, JAMES (1880 - 1925), boxer
- DRISCOLL, JIM - see DRISCOLL, JAMES
- DRYW BACH - see WILLIAMS, RICHARD
- DRYW, Y - see HUGHES, EDWARD
- DUBRICIUS Saint - see DYFRIG, Saint
- DUNAWD (fl. 6th century), saint
- DUNRAVEN, 4th Earl - see WYNDHAM-QUIN, WINDHAM THOMAS
- DUNRAVEN, 5th Earl - see WYNDHAM-QUIN, WINDHAM HENRY
- DUNSTAN (1477 - 1563), bishop - see KITCHIN, ANTHONY
- DURSTON, THOMAS (d. 1767), bookseller and printer
- DWN, HENRY (before c. 1354 - November 1416), landowner and rebel
- DWNN, GRUFFYDD (c. 1500 - c. 1570), country gentleman
- DWNN, JAMES (c. 1570 - c. 1660), poet
- DWNN, LEWYS (c. 1550 - c. 1616) Betws Cedewain, genealogist
- DWNN, OWAIN (c. 1400 - c. 1460), poet
- DYER, JOHN (1699 - 1757), poet
- DYFED - see REES, EVAN
- DYFNALLT - see OWEN, JOHN DYFNALLT
- DYFRIG (fl. 475?), saint
- DYFRIG - see DAVIES, EVAN THOMAS
- DYKINS, WILLIAM (Dirwynydd; 1831 - 1872), poet and prose-writer
- DYN DALL, Y - see DAVIES, DANIEL
- DYNEVOR, 7th Baron - see RHYS, WALTER FITZURYAN
- DYNEVOR, 8th Baron - see RHYS, WALTER FITZURYAN