Prince (formerly Prince XML) is a proprietary software program that converts XML and HTML documents into PDF files by applying Cascading Style Sheets (CSS). As technology, in electronic publishing and dynamic data-driven PDF generation, it enables the replacing of XSL-FO frameworks by CSS3 ones.
It is developed by YesLogic, a small company based in Melbourne, Australia. Marketed as a professional "XML+CSS3 to PDF" solution, it received positive reviews and was considered a unique product in the 2000s. 
In subsequent releases, CSS support was steadily extended until it was comparable with web browsers such as Opera and Mozilla Firefox. It has also been expanded to support additional platforms—the latest offering include packages for the Apple Mac, Freebsd, and Solaris platforms.
Prince was developed using the Mercury functional logic programming language.