A novel wind turbine configuration comprising of four identical rotors mounted on a single tower is studied using large-eddy simulation (LES) with turbine forces modeled using an actuator drag-disk model. The characteristics of the wakes of the multi-rotor turbine are compared to those of the wake of a conventional turbine comprised of a single rotor per tower. The single-rotor turbine has twice the diameter and the same thrust coefficient as the rotors of the multi-rotor turbine. Several multi-rotor configurations, with varying horizontal and vertical spacings between the four rotors, are evaluated. The multi-rotor turbine wakes are found to recover faster, while the turbulence intensity in the wake is smaller, compared to the wake of the conventional turbine. The mean velocity profiles obtained from the LES results are predicted accurately by a semi-analytical model assuming Gaussian radial profiles of the velocity deficits, and either linear or quadratic superposition of multiple wakes. The classical Jensen wake model, assuming top-hat radial profiles, with quadratic superposition of wakes is also found to accurately predict the decay of the axial mean velocity in the streamwise direction. The interaction between multiple multi-rotor turbines is contrasted with that between multiple single-rotor turbines by considering wind farms with five turbine units aligned perfectly with each other and the wind direction and separated by four single-rotor diameters. The wake losses are found to be significantly smaller in such a wind farm comprising of multi-rotor turbines as compared to single-rotor turbines. The top-hat analytical model is employed to quantify the benefits of the multi-rotor configuration over the conventional single-rotor configuration for a wide range of thrust coefficients and axial spacings. These results suggest that a larger planform energy flux can be achieved without significantly increased fatigue loads by using multi-rotor turbines instead of conventional, single-rotor turbines. © Published under licence by IOP Publishing Ltd.