A tunable plasmonic directional coupler is proposed based on the electro-optical control of a nematic liquid-crystal layer placed above two side-coupled gold stripe waveguides. It is shown that by proper adjustment of the structural parameters and the control voltage, the coupling length of the structure and the effective modal index of the individual waveguides can be tuned, allowing for the design of electro-optical liquid-crystal plasmonic directional coupler switches.