LaTex is a document preparation system for the Tex typesetting program. It offers programmable desktop publishing features and extensive facilities for automating most aspects of typesetting and desktop publishing, including numbering and cross-referencing, tables and figures, page layout, bibliographies, and much more. LaTex is a macro package, which sits on top of Tex and provides all the structuring facilities to help with writing large documents. Latex was originally written in 1984 by Leslie Lamport.

LaTex allows the separation of formatting from content, whilst still allowing manual typesetting adjustments where needed. It is a great help to the authors who can now concentrate on writing within the logical structure of their document rather than spending their time on the details of formatting.

LaTex was originally most commonly used by mathematicians and scientists amongst whom it remains the favored tool for writing papers, preprints and books. The popularity of LaTex in the technical and academic communities is perhaps partly due to its early availability on Unix systems, and the comparative unavailability of competing word processors on those platforms until recently.

However, it remains less popular outside the technical communities. It is regarded as hard to learn for people with no prior experience of mark up languages.

LaTex is a free software and it is usually pronounced "LAY-tech" or "LAH-tech".