MoS2 and montmorillonite (MMT) nanosheets were hybridized through a simple in-situ hydrothermal synthesis in order to develop an efficient adsorbent, MoS2/MMT composite, for the removal of mercury from water. Raman, XRD, and FTIR results displayed the good hybridization of MMT and MoS2. HRTEM images indicated that the active edges of MoS2 were clearly exposed in the hybrid, demonstrating the vital role of MMT as eco-friendly, cheap and stable substrate for the growth of MoS2. The overall adsorption process of Hg2+ on MoS2/MMT proved that the composite is highly efficient for the removal of Hg2+ from water, adsorbing up to 1836 mg/g of Hg2+, which outperformed most literature reported adsorbents. The adsorption kinetic and isotherm models could be well described by pseudo-first-order and Langmuir models, respectively. Furthermore, the Langmuir dimensionless constant, RL show that Hg2+ adsorption on the composite was found favorable to occur at the temperature of 25 °C and 35 °C. The XPS analysis revealed that the S sites and slight O sites were main contributors for the remarkable adsorption performance of MoS2/MMT composite on Hg2+ removal. This work suggests that MoS2 supported on MMT substrate might be a promising adsorbent with high capacity and super efficiency for the removal of heavy metals from aqueous solution. Display omitted •Preparation of MoS2/MMT composite through a simple in-situ hydrothermal method.•Efficient adsorptive removal of Hg2+ from water.•Investigation of kinetics and isotherm model.•Montmorillonite as supporting material to improve the dispersibility of MoS2 in water.•Elucidating the underlaying adsorption mechanism.