| IBM Advanced BASIC | — | 1981 | — |
| IBM BASIC | — | 1981 | IBM |
| IBM Cross System Product | — | — | IBM |
| IBM Informix-4GL | — | 1986 | IBM |
| IBM PL/S | — | — | IBM |
| IBM RPG II | — | 1965 | IBM |
| IBM RPG III | — | 1978 | IBM |
| IBM System/36 BASIC | — | — | IBM |
| ICI | — | — | — |
| Icon | procedural programming, structured programming, expression-oriented programming, multi-paradigm programming | 1977 | — |
| ICon-L | — | 1994 | — |
| Id | — | 1975 | — |
| Idris | purely functional programming, functional programming, total functional programming | 2007 | — |
| Illumination Software Creator | — | — | — |
| ILNumerics.Net | object-oriented programming | — | — |
| Imba | — | 2012 | — |
| Impromptu | functional programming | 2005 | — |
| Impulse C | — | 2003 | — |
| Incr Tcl | object-oriented programming, event-driven programming, functional programming, imperative programming | 1993 | Michael McLennan |
| Inform | procedural programming, object-oriented programming, declarative programming | 1993 | Graham Nelson |
| Information Processing Language | procedural programming | 1956 | Cliff Shaw, Herbert Simon, Allen Newell |
| Ink | — | — | Inkle |
| Installer | — | — | — |
| Integer BASIC | — | 1977 | Steve Wozniak |
| Intel Parallel Building Blocks | imperative programming | 2010 | Intel |
| Interactive C | — | 1997 | — |
| Interactive Data Language | array programming | 1977 | — |
| INTERCAL | esoteric programming | 1972 | — |
| Interlisp | — | 1967 | — |
| Intermediate Programming Language | — | 1951 | — |
| Internal Translator | — | 1955 | — |
| Interpress | — | — | Palo Alto Research Center |
| InterSystems Caché | — | — | InterSystems |
| Io | object-oriented programming, prototype-based programming | 2002 | Steve Dekorte |
| Ioke | prototype-based programming | 2008 | Ola Bini |
| Iota and Jot | esoteric programming | — | Chris Barker |
| IRIS (AI orchestrator) | — | — | CAI Technology |
| IronLisp | — | — | — |
| IronScheme | — | — | — |
| ISLISP | reflective programming, object-oriented programming, metaprogramming, functional programming, procedural programming | 1997 | — |
| ISWIM | imperative programming, functional programming | 1966 | — |
| Itk | multi-paradigm programming | 1993 | — |
| Ixi lang | — | — | Ixi software |