The invention relates to a bipolar plate for a fuel cell, comprising an anode plate with anode gas channels and a cathode plate with cathode gas channels, said plates having an active region and supply regions and being arranged one over the other such that the gas channels form coolant channels. The aim of the invention is to improve such a bipolar plate such that the flow conditions of reactants and coolant in the bipolar plate are optimized. This is achieved in that the height and/or the width of the cathode gas channels increase(s) from a first side of the active region to a second side of the active region, and the height and/or the width of the anode gas channels decrease(s) from the first side of the active region to the second side of the active region, wherein the cross-sectional area and/or the hydraulic diameter of the cathode gas channels increases, and the cross-sectional area and/or the hydraulic diameter of the anode gas channels decreases. The invention additionally relates to a fuel cell stack and to a vehicle.