Over the last years, a great deal of ontologies of many different kinds and describing different domains has been created, and new methods and prototypes have been developed to search them easily. These ontologies may be reused for several tasks, such as for increasing semantic interoperability, improving searching, supporting Information Systems or the creation of their conceptual schemas. Searching an ontology that is relevant to the users’ purpose is a big challenge, and when the user is able to find it a new challenge arises: how to adapt the ontology in order to be applied effectively into the problem domain. It is nearly impossible to find an ontology that can be applied as is to a particular problem. Is in that context where ontology refactoring takes special interest. This chapter tries to clarify what ontology refactoring is and presents a possible catalog of ontology refactoring operations.