Abstract. One of the main difficulties during the design of collaborative learning activities is adequate group formation. In any type of collaboration, group formation plays a critical role in the learners' acceptance of group activities, as well as the success of the collaborative learning process. Nevertheless, to propose both an effective and pedagogically sound group formation is a complex issue due to multiple factors that influence group arrangement. The current (and previous) learner's knowledge and skills, the roles and strategies used by learners to interact among themselves, and the teacher's preferences are some examples of factors to be considered while forming groups. To identify which factors are essential (or desired) in effective group formation, a well structured and formalized representation of collaborative learning processes, supported by a strong pedagogical basis, is desirable. Thus, the main goal of this paper is to present an ontology that works as a framework based on learning theories that facilitates group formation and collaborative learning design. The ontology provides the necessary formalization to represent collaborative learning and its processes, while learning theories provide support in making pedagogical decisions such as gathering learners in groups and planning the scenario where the collaboration will take place. Although the use of learning theories to support collaborative learning is open for criticism, we identify that they provide important information which can be useful in allowing for more effective learning. To validate the usefulness and effectiveness of this approach, we use this ontology to form and run group activities carried out by four instructors and twenty participants. The experiment was utilized as a proof-of-concepts and the results suggest that our ontological framework facilitates the effective design of group activities, and can positively affect the performance of individuals during group learning.