Inflammatory bowel disease (IBD) is a chronic systemic inflammatory condition. Previously, the focus has been on extraintestinal manifestations of IBD, including arthritis, psoriasis, and uveitis. Although comorbidities have long been the subject of intensive research in other chronic inflammatory diseases such as rheumatoid arthritis, the concept of comorbidities is only beginning to emerge in IBD. Several comorbid conditions have been proposed to be related to IBD, including cardiovascular disease, neuropsychological disorders, and metabolic syndrome. Recognition of these conditions and their treatment could lead to better management of IBD. This Review aims to explore current knowledge regarding classic and emerging comorbidities related to IBD. Copyright © 2019 Elsevier Ltd. All rights reserved.