The DISAGROUP project has investigated the phenomenon of complex disagreement in society from a philosophical perspective. Social epistemology has been mainly devoted to the study of peer disagreement (the kind of disagreement among individuals who share the same evidence and intellectual capacities). However, real-life disagreements such as long-standing religious, political or economic disagreements have a much more complex structure: the involved parties are not normally individual epistemic peers but groups that do not possess the same evidence or intellectual resources, they involve a lot of claims and are usually sustained not for the sake of knowledge but by elements such as faith, hate, intolerance or distrust. DISAGROUP has filled a gap in the philosophical literature by giving a general account of the structural elements that make most real-life disagreements so complex and difficult to understand, with a particular focus on the role played by groups in sustaining complex disagreements.