IT Infrastructure Library (ITIL) has become the
standard for IT Service Management (ITSM). Despite the advantages in the adoption of ITIL’s best practices, some problems have been identified: different interpretations due to the complexity of concepts with poor specification and formalization; different approaches to the same problems; difficulties exchanging process models in different process model languages. Besides all published work, is still missing a metamodel expressing the core concepts, their relationship, and constraints. In this paper, we propose an ITIL metamodel to reduce conceptual and terminological ambiguity, addressing the identified problems, namely: (1) describing the core concepts of ITIL to be used by other approaches; (2) allowing the integration, exchange, sharing and reutilization of models; and (3) the use of different modelling languages following the defined principles.