| Saint | Background | Date | Feast Day |
| Iban | 02/08 | ||
| Ibor/Ibar/Ivor/Ivar McLugni | of Beggerin Island (Iberius, Bishop of Meath) | 23/04 | |
| Ida | of Herzfeld | 04/09 | |
| Idaberga/Edberge | 20/06 | ||
| Ide | 15/01 | ||
| Idus | Bishop of Leinster | 14/07 | |
| Ignatios | the New Martyr | d1814 | (Orth) 08/10 |
| Ignatius.Inigo (of) Loyola | Loyola, Jesuit founder, 1491-1556 | 1491-1556 | 31/07 (13/07) |
| Ignatius | 12/05 | ||
| Ignatius | 16/12, 17/12 | ||
| Ignatius | 20/12 | ||
| Ignatius | 31/01 | ||
| Ignatius | Bishop of Antioch (Theophoros/God-Bearer) martyr | d c107 | 01/02 17/10 |
| Ignatius | Bishop of Constantinople | 23/10 | |
| Ildephonsus | Archbishop of Toledo | c607-67 | 23/01 |
| Illadan | Bishop of Rathlihen, Ireland | 10/06 | |
| Illidius | Bishop of Auvergne | (Translation) 13/12 | |
| Illidius | Bishop of Clermont | 05/06 | |
| Illogan | Irish missionary | C6th | 30/10 |
| Illtyd/Illtud | Founder of Llanilltud Fawr/ Llantwit Major | C6th | 06/11 07/07 |
| Illud(iana)/Juliot/Julitta | of Luxulyon, Cornwall, dau Brychan | C6th | 29/06 |
| Imana | of Loss | 21/10 | |
| Imelda Lambertini | of Bologna | 1322-33 | 13/05 (12/05) |
| Ina + Queen Ethelburga | King of Wessex/the West Saxons | C8th | 06/02 08/09 |
| Indract(us) + comps | King of Ireland | 08/05 | |
| Indractus his sister Dominica + 9 comps | hermit, Glastonbury | 05/02 | |
| Inez de Beniganim, Blessed (Josepha Maria of St. Agnes) | Augustinian hermitess | 21/01 | |
| Ingenuinus + Albuinus | 05/02 (Trans 13/05) | ||
| Ingrid | of Sweden, Dominican nun | d1282 | 02/09 |
| Inigo | Hermit, Abbot at Ona, Spain | d1057 | 01/06 |
| Innocent | 22/06 | ||
| Innocent I | Pope | 28/07 (09/12, 14/03) | |
| Innocent XI, Blessed | Pope | 12/08 | |
| Innocentia | 05/09 | ||
| Invelta | 15/04 | ||
| Iomhar | 12/08 | ||
| Ionius | 03/08 | ||
| Irais | of Alexandria | 22/09 | |
| Irchard | See 'Yrchard' | 24/08 | |
| Irenaeus | Bishop of Lyon | d c202 | 28/06 |
| Irenaeus | Bishop of Sirmium | 24/03 | |
| Irenaeus/Ireneus + comps | 03/08 27/06 | ||
| Irene | 12/08 | ||
| Irene | of Santarem | 20/10 | |
| Irene | Empress | d803 | 05/04 |
| Irene, Agape + Chione | Martyrs, Macedonia | d304 | 03/04 |
| Irmina + Adela | Dau King/St Dagobert II, nun at Treves & Weissenburg | C8th | 24/12 |
| Isaac | 11/04 | ||
| Isaac | 16/03 | ||
| Isaac | of Cyprus | 21/09 | |
| Isaac | the Great, Catholicos of Armenia | d439 | 09/09 |
| Isaac Jogues + Rene Goupil | martyred by the Huron | d 1640s | |
| Isabel | of France, dau Louis VIII, nun at Longchamps | C13th | 26/02 |
| Isabel | 31/08 | ||
| Isadora | 01/05 | ||
| Isadore | of Antioch | 02/01 | |
| Isadore | of Nitria | 2/1 | |
| Isadore | of Seville, Doctor of the Church | d636 | 04/04 |
| Ischyrion + Chaeremon | C3rd | 22/12 | |
| Ishmael/Ismael | Bishop of Menevia, Wales | C7th | 16/06 |
| Isidore | 25/10 | ||
| Isidore | of Pelusium (Mount Pelousion) | ||
| Isidore | the Farmer, Madrid | C12th | 15/05 (10/05) |
| Isidore | Bishop of Seville | 15/01, 07/01 | |
| Isidore | Martyr | 07/01 | |
| Isidore | Priest | 15/01 | |
| Ita/Ida/Mida/Dorothy/Deirdre | of Killeedy, foster-mother of Brendan | d570 | 15/01 |
| Iterius | Bishop of Nevers | 25/06 | |
| Ithamar | Bishop of Rochester | 10/06 | |
| Itisberga | Virgin | 21/05 | |
| Ives/Ia | virgin martyr, Cornwall | 03/02 | |
| Ivetta | See 'Yvette' | 13/01 | |
| Ivo | Bishop of Chartres | C11th | 20/05 23/05 23/12 (Trans 28/10) |
| Ivo/Ives/Ive/Yvo | Bishop of Huntingdonshire | 24/04 25/04 | |
| Ivo/Yvo/Yves | priest at Kermartin, Tréguier | 1253-1303 | 22/05 19/05(Translation 27/10) |
| Ivor | 19/05 | ||
| Iwi(gius)/Ywi | of Lindisfarne | d c690 | 08/10 |
This collection of names was compiled by Kate Monk and is ©1997, Kate Monk.
Copies may be made for personal use only.