- I. D. FFRAID - see EVANS, JOHN
- IACO ab DEWI - see DAVIES, JAMES
- IACO ap DEWI - see DAVIES, JAMES
- IAGO ab IDWAL ap MEURIG (d. 1039), king of Gwynedd
- IAGO ab IDWAL FOEL (fl. 942-979), king of Gwynedd
- IAGO ap DEWI - see DAVIES, JAMES
- IAGO ap DEWI - see DAVIES, JAMES
- IAGO ap IAGO - see JAMES, JAMES
- IAGO ap IEUAN - see JAMES, EVAN
- IAGO BENCERDD - see HUGHES, JAMES
- IAGO EMLYN - see JAMES, JAMES
- IAGO ERFYL - see JAMES, THOMAS DAVIES
- IAGO MOCHNANT - see JONES, JAMES
- IAGO TRICHRUG - see HUGHES, JAMES
- IANTO'R CASTELL - see BEVAN, EVAN
- IDRIS FYCHAN - see JONES, JOHN
- IDRISON - see PUGHE, WILLIAM OWEN
- IDRISWYN - see THOMAS, EDWARD
- IDRISYN - see JONES, JOHN
- IDWAL ab IDWAL FOEL - see IEUAF ab IDWAL FOEL
- IDWAL ap MEURIG (d. 996), prince of Gwynedd
- IDWAL FOEL (d. 942), king of Gwynedd
- IESTYN ap GWRGANT (fl. c. 1081-1093), last independent ruler of Glamorgan
- IEUAF (or IDWAL) ab IDWAL FOEL (d. 985), joint king of Gwynedd
- IEUAN (d. 1137), archpresbyter - see SULIEN
- IEUAN ab EDNYFED ap HYWEL (d. 1403) - see WYNN
- IEUAN ap BEDO GWYN (fl. c. 1530-1590?), poet
- IEUAN ap GRUFFUDD LEIAF (fl. latter half of 15th century), poet
- IEUAN ap HUW CAE LLWYD (fl. 1475-1500), one of the minor poets of the 15th century
- IEUAN ap HYWEL SWRDWAL (fl. 1430-1480), poet
- IEUAN ap IAGO - see JAMES, EVAN
- IEUAN ap IEUAN ap MADOG (fl. 1547-1587), scribe
- IEUAN ap LLYWELYN FYCHAN (d. 1532), poet
- IEUAN ap MADOG ap DAFYDD (fl. c. 1500), poet
- IEUAN ap MAREDUDD ap HYWEL ap DAFYDD ap GRUFFYDD Cefn-y-Fan, Cesail Gyfarch (d. 1403) - see WYNN
- IEUAN ap RHISIART - see PRITCHARD, EVAN
- IEUAN ap RHYDDERCH ap IEUAN LLWYD (fl. 1430-1470), gentleman and poet
- IEUAN ap RHYS ap LLYWELYN (fl. beginning of 16th century), poet
- IEUAN ap ROBERT ap MAREDUDD Cesail Gyfarch (1437 - 1468) - see WYNN
- IEUAN (IFAN) ap SION (fl. c. 1612-1636), poet
- IEUAN ap TUDUR PENLLYN (fl. c. 1480), poet
- IEUAN AWST - see PUGH, JOHN
- IEUAN BEDO GWYN - see IEUAN ap BEDO GWYN
- IEUAN BLAENAU - see BLAYNEY
- IEUAN BRECHFA (c.1430 - 1500), poet and genealogist
- IEUAN BRYDYDD HIR - see EVANS, EVAN
- IEUAN BRYDYDD HIR HYNAF (fl. c. 1450), poet
- IEUAN BUALLT - see JONES, EVAN
- IEUAN CADFAN - see BREEZE, EVAN
- IEUAN CLYWEDOG (fl. 1577-1596), poet