| Place name | Origin & meaning | Source |
| Illalong | Early name for Morpeth given by Lt E.C.Close in 1821 after the aboriginal name for the region meaning swampy plain or a resort for brolgas. By 1823 there are references to a small settlement at Illalung but by 1827 the name had ceased being used. | NHDHS: Ports and People |
| Illulaung | Aboriginal - name for Green Hills, later Morpeth | NMH 24.12.1976 |
| Industrial Close (Muswellbrook) | Industrial subdivision by Department of Lands on former common. | Muswellbrook Chronicle 28.01.1983. |
| Industrial Highway (Mayfield) | Named due to the fact that it was constructed through land owned by B.H.P. | NMH 26.02.1970. |
| Inglewood | Proposed name for Awaba School in 1887 but later changed to Grenton as the name had previously been used. | Saxon,D: Pit Props and Sleepers. |
| Invermein | Early name for Scone in the official records of the Benches of Magistrates. The name like those of a lot of the neighbouring properties came from Scotland. | Journal of H.V.History Vol 2 no 1 p81. |
| Ireland Avenue (Waratah) | From H.J. Ireland, Aldrman Waratah Council, 1920. | Waratah Public School Cent. Book. |
| Irishtown | Early name for the area around the Mill Brook estate c 1850's - 1860's, due to the large number of Irish tenants who lived there. . | Glen William Sesquicentenary Book p 5 |
| Irishtown ( Lochinvar) | Site opposite Dalwood vineyards, part of property "Knockfin". | Boyle's Lower Hunter INdex. |
| Irishtown (Maitland) | Colloquial name for area around Maitland. | Harry Boyle 16.01.1996 |
| Ironbark | Name given by Lt Platt to his property extending south from the river to Platt Strewet, Warath adn west from Tourle Street, Mayfield to Ironbark Creek, Sandgate. | NHDHS: Ports and People |
| Ironbark Road (Muswellbrook) | Native flora. | Muswellbrook Chronicle 28.01.1983. |
| Irrawang | Reference to the property that was in the area. Aboriginal - where the water runs. | MM 23.11.1865. |
| Irrawang Street (Raymond Terrace) | After James King's estate. | Hunter,C: History and Heritage. |
| Irving Street ( Beresfield) | Allegedly named so that subdivider's children wouldn't forget their English literature/science or alphabet | D. Smith, Hawthorne Street Beresfield |
| Irving Street (Wallsend) | After Clark Irving, a director of the Newcastle Wallsend Coal Company. Formerly known as Irvine Street. | Wallsend Digest 29.08.1963. |
| Isis River (Murrurundi) | After the name of the upper waters of the river Thames, London. | NMH24.12.1953 |
| Isis Way (Muswellbrook) | A tributary of the Pages River. | Muswellbrook Chronicle 28.01.1983. |
| Islington | After a suburb of London, which was the home of Mr J.H.Hubbard the developer of the subdivision that now bears his name. | Social Sciences Teacher Vol13 no5 30.11.1983 |
| Isobella Street (Muswellbrook) | Wine industry theme. | Muswellbrook Chronicle 28.01.1983. |