OCaml was created in 1996 by Xavier Leroy, Jérôme Vouillon,[5] Damien Doligez, Didier Rémy,[6] Ascánder Suárez, and others.

OCaml was initially developed in the context of automated theorem proving, and is used in static analysis and formal methods software.

Beyond these areas, it has found use in systems programming, web development, and specific financial utilities, among other application domains.

[7] OCaml is a free and open-source software project managed and principally maintained by the French Institute for Research in Computer Science and Automation (Inria).

Effective use of OCaml's type system can require some sophistication on the part of a programmer, but this discipline is rewarded with reliable, high-performance software.

Xavier Leroy has stated that "OCaml delivers at least 50% of the performance of a decent C compiler",[8] although a direct comparison is impossible.

Milner repeatedly ran into the issue that the theorem provers would attempt to claim a proof was valid by putting non-proofs together.

Guy Cousineau, a researcher at Paris Diderot University, recognized that this could be applied as a compiling method for ML.

[12] Guy Cousineau is quoted recalling that his experience with programming language implementation was initially very limited, and that there were multiple inadequacies for which he is responsible.

Despite this, he believes that "Ascander, Pierre and Michel did quite a nice piece of work.”[12] Between 1990 and 1991, Xavier Leroy designed a new implementation of Caml based on a bytecode interpreter written in C. In addition to this, Damien Doligez wrote a memory management system, also known as a sequential garbage collector, for this implementation.

[12] In the following years, libraries such as Michel Mauny's syntax manipulation tools appeared and helped promote the use of Caml in educational and research teams.

[11] Didier Rémy and Jérôme Vouillon designed an expressive type system for objects and classes, which was integrated within Caml Special Light.

In 2000, Jacques Garrigue extended Objective Caml with multiple new features such as polymorphic methods, variants, and labeled and optional arguments.

[11][12] Language improvements have been incrementally added for the last two decades to support the growing commercial and academic codebases in OCaml.

[11] The OCaml 4.0 release in 2012 added Generalized Algebraic Data Types (GADTs) and first-class modules to increase the flexibility of the language.

[11] The OCaml 5.0.0 release in 2022[13] is a complete rewrite of the language runtime, removing the global GC lock and adding effect handlers via delimited continuations.

OCaml features a static type system, type inference, parametric polymorphism, tail recursion, pattern matching, first class lexical closures, functors (parametric modules), exception handling, effect handling, and incremental generational automatic garbage collection.

A foreign function interface for linking to C primitives is provided, including language support for efficient numerical arrays in formats compatible with both C and Fortran.

The OCaml distribution contains: The native code compiler is available for many platforms, including Unix, Microsoft Windows, and Apple macOS.

OCaml bytecode and native code programs can be written in a multithreaded style, with preemptive context switching.

MetaOCaml[24] is a multi-stage programming extension of OCaml enabling incremental compiling of new machine code during runtime.