A device is proposed for the UV disinfection of liquids in an open or closed channel, having an inflow for the liquid to be disinfected, at least one UV irradiator arranged downstream of the inflow in a main flow direction and also having an outflow arranged downstream of the UV irradiator, in which a mixing device, driven by an electric motor, is arranged between the inflow and the at least one UV irradiator, which mixing device is set up for generating a cross-flow having at least one velocity component transverse to the main flow direction in order to improve mixing of the liquid.