| Abbreviation | Definition |
|---|---|
| IGHR | Institute of Genealogy and Historical Research |
| IGHR | Institute of Genealogy Historical Research |
| IGI | International Genealogical Index |
| IGP | Ireland Genealogy Project |
| IGP | Ireland Genealogy Projects |
| IGRA | Israel Genealogy Research Association |
| incl | including |
| INF | INFancy |
| inf | infant;infancy |
| inf. | infant |
| INT | INTestate |
| int | intestate, without will |
| IORM | Improved Order of Red Men |
| IPM | Inquisition Post Mortem |
| ISANNZ | Irish Studies Association of Australia and New Zealand |
| ISBGFH | International Society for British Genealogy and Family History |
| ISFHWE | International Society of Family History Writers and Editors |
| Iss. | issue [offspring] |
| IUI | Intra Uterine Insemination |
| j.m. | jure matris (in the right of one's mother) |