Jean-Laurent Casanova is pediatrician and immunologist by training, and has in practice become a human geneticist investigating the immunological basis of childhood infectious diseases. He has been recognized for his paradigm‐shifting discoveries, demonstrating that life-threatening infectious diseases striking otherwise healthy children may be caused by single‐gene inborn errors of immunity, including variations underlying mycobacterial diseases (IFN‐γ immunity), invasive pneumococcal disease (TIR), herpes simplex virus encephalitis (TLR3), and chronic mucocutaneous candidiasis (IL‐ 17). Casanova was born in Paris, France, in 1963. He received his MD from the University of Paris Descartes in 1987, and his PhD in immunology from the University of Paris Pierre and Marie Curie in 1992, after being trained at the Pasteur Institute in Paris and the Ludwig Institute for Cancer Research in Lausanne. Following a residency in pediatrics and a clinical fellowship in pediatric immunology-hematology, he was appointed a professor of pediatrics at the Necker Medical School in Paris. There, with Laurent Abel, he cofounded and codirected the Laboratory of Human Genetics of Infectious Diseases in 2001. He was appointed professor at Rockefeller in 2008 and named a Howard Hughes Medical Institute investigator in 2014. He is a member of both the National Academy of Sciences and the National Academy of Medicine.