| Ladder logic | visual programming language | — | — |
| Language H | procedural programming | 1962 | — |
| Laning and Zierler system | — | 1954 | — |
| Lasso | structured programming, procedural programming, object-oriented programming, concurrent computing | 1995 | — |
| Lava | visual programming language, object-oriented programming | — | — |
| Lazy ML | — | 1984 | — |
| LC-3 | — | — | Yale Patt |
| Le Lisp | — | — | Institut National de Recherche en Informatique et en Automatique |
| Lean | functional programming | 2013 | Microsoft Research, Leonardo de Moura |
| Lean 3 file format | — | — | — |
| Lean 4 file format | — | — | — |
| Lean file format family | — | — | — |
| Leda | — | 1995 | — |
| Leet | — | — | — |
| LEGO | — | — | — |
| LETA (AI assistant) | — | — | CAI Technology |
| Level I BASIC | — | 1977 | — |
| Lexico | — | 1985 | — |
| LFE | functional programming | 2008 | — |
| Liberty BASIC | event-driven programming | 1992 | — |
| Light.vn | — | — | — |
| Limbo | concurrent computing, modular programming | 1995 | Bell Labs |
| Linda | — | 1985 | David Gelernter |
| Linden Scripting Language | — | — | Linden Lab |
| Lingo | object-oriented programming | 1989 | John Thompson |
| Links | — | 2006 | Philip Wadler |
| Linotte | object-oriented programming | 2005 | — |
| Lioness | — | — | — |
| LIPS | — | 2018 | Jakub T. Jankiewicz |
| Liquidsoap | — | — | — |
| LIS | procedural programming | 1973 | — |
| LISA | — | 1997 | — |
| Lisaac | object-oriented programming | 2003 | — |
| Lisp | multi-paradigm programming, functional programming, procedural programming, reflective programming, metaprogramming | 1958 | John McCarthy, Steve Russell |
| Lisp Machine Lisp | object-oriented programming | 1976 | — |
| Lisp-based Intelligent Software Agents | — | — | — |
| LispWorks | — | — | — |
| Lite-C | — | 2007 | — |
| Lithe | declarative programming | 1982 | — |
| Little b | object-oriented programming, functional programming | 2004 | Harvard Medical School |
| Little Smalltalk | — | — | Timothy Budd |
| LiveCode | object-oriented programming | 2001 | LiveCode |
| LiveScript | functional programming, object-oriented programming | 2011 | George Zahariev, Jeremy Ashkenas, Satoshi Murakami |
| LiveScript | — | — | Netscape |
| Locomotive BASIC | — | 1984 | Locomotive Software |
| Lodu Code | — | — | Prince Kumar Pandit |
| Logic Basic | — | — | — |
| Logica | — | — | — |
| Loglan | object-oriented programming | — | — |
| Logo | functional programming, procedural programming, reflective programming | 1967 | Cynthia Solomon, Idit Harel Caperton, Seymour Papert |
| Logtalk | prototype-based programming, logic programming, object-oriented programming | 1998 | — |
| LOLCODE | structured programming, procedural programming, imperative programming | 2007 | — |
| LOOM | declarative programming, knowledge representation and reasoning | — | — |
| LotusScript | object-oriented programming | — | — |
| LPC | object-oriented programming, procedural programming, prototype-based programming, functional programming | 1989 | Lars Pensjö |
| LSE | procedural programming, structured programming | — | Supélec |
| Lua | procedural programming, prototype-based programming, functional programming, imperative programming, multi-paradigm programming, object-oriented programming | 1993 | Roberto Ierusalimschy |
| Luau | — | — | — |
| Lucee | — | 2015 | — |
| Lucid | dataflow programming, concurrent computing, reactive programming, declarative programming | 1976 | — |
| Luna | — | 2011 | — |
| Lush | — | — | — |
| Lustre | synchronous programming, declarative programming, dataflow programming | — | — |
| LYaPAS | functional programming, structured programming, array programming, modular programming | 1964 | — |
| Lynx | — | 1984 | University of Wisconsin–Madison |