Steam locomotives operated in the United Kingdom with names beginning with I.
| Name | Railroad, # | Builder, s/n | Build date | Whyte type | Notes |
|---|---|---|---|---|---|
| I. T. Williams | LNWR 155 | Crewe | 3/1917 | 4-6-0 | Rn Sir Thomas Williams in December 1919; became LMS 5932; wd 4/1935. |
| Iago | GWR | 0-6-0ST | |||
| Ickenham Hall | GWR 5944 | 4-6-0 | |||
| Ilion | LNWR 526 | Crewe 4537 | 3/1906 | 4-4-0 | Became LMS 5238; wd 12/1928. |
| Illustrious | LMS 5532 | 4-6-0 | |||
| Illustrious | LNWR 150 | Crewe | 3/1921 | 4-6-0 | Became LMS 6011; wd 2/1933. |
| Illustrious | LNWR 1956 | 2/1902 | 4-4-0 | Transferred to LMS; wd 1/1923. | |
| Imberhorne | LBSCR 327 | 12/1880 | 2-2-2 | Wd 4/1910. | |
| Immingham | LNER 6097 | 4-6-0 | |||
| Impala | LNER 8303 | 4-6-0 | |||
| Implacable | LMS 5709 | 4-6-0 | |||
| Implacable | LNWR 1915 | 6/1899 | 4-4-0 | Became LMS 5114; rb 11/1923. | |
| Impregnable | LMS 5721 | 4-6-0 | |||
| Inchcape | GWR 3430 | 4-4-0 | |||
| India | LMS 5574 | 4-6-0 | |||
| India | LNWR 868 | 6/1911 | 4-4-0 | Became LMS 5350; rn 25350; became BR 58011; wd 5/1948. | |
| Indomitable | LMS 5720 | 4-6-0 | |||
| Indore | LMS 5592 | 4-6-0 | |||
| Industry | B&GR | 2-4-0 | |||
| Inflexible | LMS 5727 | 4-6-0 | |||
| Inflexible | LNWR 1917 | 7/1899 | 4-4-0 | Rb 8/1922; became LMS 5184. | |
| Ingestre | LMS 5945 | Crewe | 6/1917 | 4-6-0 | Built as LNWR 2420; named 1/1923; wd 4/1934 |
| Inkermann (1st) | GWR | 4-2-2 | |||
| Inkermann (2nd) | GWR | 4-2-2 | |||
| Intrepid | LNWR 1922 | 2/1900 | 4-4-0 | Rb 10/1916; became LMS 5146. | |
| Inverness-shire | LNER 329 | 4-4-0 | |||
| Invincible | LMS 5715 | 4-6-0 | |||
| Invincible | LNWR 1914 | 6/1899 | 4-4-0 | Rb 9/1916; rn #1257 in 4/1920; became LMS 5144. | |
| Ionic | LNWR 1312 | Crewe 4532 | 2/1906 | 4-4-0 | Became LMS 5242; wd 11/1930. |
| Iris | GWR | 0-6-0 | |||
| Irish Free State | LMS 5572 | 4-6-0 | |||
| Irish Guardsman | LMS 6116 | 4-6-0 | |||
| Iron Duke | 4-2-2 | Operable replica of GWR's first Iron Duke locomotive. | |||
| Iron Duke | BR 70014 | Crewe | 6/1951 | 4-6-2 | Wd 12/1967; scr 4/1968. |
| Iron Duke (1st) | GWR | 4-2-2 | |||
| Iron Duke (2nd) | GWR | 4-2-2 | |||
| Iron Duke | LNWR 1903 | 3/1899 | 4-4-0 | Became LMS 5110; rb 5/1924. | |
| Ironside | SR 3458 | 0-4-0ST | |||
| Irresistible | LMS 5710 | 4-6-0 | |||
| Irresistible | LNWR 1916 | 7/1899 | 4-4-0 | Rb 2/1919; became LMS 5155. | |
| Isabella | LNWR 403 | Crewe | 4/1892 | 2-4-0 | Wd 9/1922. |
| Isambard Kingdom Brunel | GWR 5069 | 4-6-0 | |||
| Iseult | BR 73116 | Doncaster | 11/1956 | 4-6-0 | Wd 11/1964; scr 2/1965 at Eastleigh. |
| Iseult | SR 749 | 4-6-0 | |||
| Isinglass | LNER 2562 | 4-6-2 | |||
| Isle of Jersey | GWR 3284 | 4-4-0 | |||
| Isle of Man | LMS 5511 | 4-6-0 | |||
| Ivanhoe | GWR | 4-4-0 | |||
| Ivanhoe | GWR 2980 | 4-6-0 | |||
| Ivanhoe | LNER 9339 | 4-4-0 | |||
| Ixion | GWR | 2-2-2 | |||
| Ixion | SDR | St&Sl | 1853 | 4-4-0ST | Involved in a collision with Comet on August 1, 1853; became GWR 2105 in 1876. |