Type 1 diabetes (T1D) is an organ‐specific autoimmune disease in which the insulin‐producing β cells in the pancreatic islets are selectively eliminated. T cells specific for β‐cell antigens are the mediators of this precise cellular destruction. However, antibodies to β‐cell proteins are also generated and may be used for predicting disease in at‐risk populations. Over the past two decades, numerous β‐cell proteins and lipids have been implicated as autoantigens in patients or in non‐obese diabetic (NOD) mice, a well‐studied animal model of T1D. Here, we present a review of these antigens, accompanied by their T‐cell epitopes, where known, and a discussion of our current understanding of why particular self‐proteins become disease‐inciting antigens. Although two dozen β‐cell antigens have been identified to date, few of these have been confirmed to be recognized by pathogenic T cells early in the disease process. Further identification and characterization of initiating β‐cell antigens targeted by pathogenic T cells should be a priority for future studies.