This manual documents the release 5.3 of the OCaml system. It is organized as follows. Part I, “An introduction to OCaml”, gives an overview of the language. Part II, “The OCaml language”, is the reference description of the language. Part III, “The OCaml tools”, documents the compilers, toplevel system, and programming utilities. Part IV, “The OCaml library”, describes the modules provided in the standard library. Volume 1 covers Parts I, II, and III. Volume 2 covers Part IV. The full Table of Contents and appropriate indices are included in each published volume.