This review summarizes recent advances in understanding the genetics and pathogenesis of inflammatory bowel disease (IBD). Genome-wide association studies have identified over 100 genetic risk loci for IBD, with about 30% shared between Crohn's disease and ulcerative colitis. These loci implicate biological pathways important for intestinal homeostasis such as barrier function, innate immune regulation, and response to microbes. Genetic variants can interact with environmental factors like smoking to influence IBD development through specific mechanisms. The review discusses candidate IBD genes in the context of relevant molecular pathways and how genetics studies continue providing insight into the complex interplay between host genetics and environmental cues in IBD.