Henri B\'enard: Thermal convection and vortex shedding

We present in this article the work of Henri B\'enard (1874-1939), French physicist who began the systematic experimental study of two hydrodynamic systems: the thermal convection of fluids heated from below (the Rayleigh-B\'enard convection and the B\'enard-Marangoni convection) and the periodical vortex shedding behind a bluff body in a flow (the B\'enard-K\'arm\'an vortex street). Across his scientific biography, we review the interplay between experiments and theory in these two major subjects of fluid mechanics.