OWLTools is a library for working with OWL-format ontologies. It provides functionality to support the Gene Ontology (GO) and other ontology projects, offering convenience methods on top of the OWL API. OWLTools includes the OBO Ontology Release Tool (OORT) a command-line tool for releasing OWL- and OBO-format ontologies.

Over time, some of the functionality of OWLTools is being taken over by ROBOT.