This letter reports the polymer passivation of field plated lateral β-Ga 2 O 3 MOSFETs with significant improvement in the breakdown voltages as compared to non-passivated devices. We show consistent results of higher breakdown voltages in passivated devices as compared to non-passivated devices for MOSFETs with Lgd ranging from 30μm to 70μm and across two process runs. We obtain a record high breakdown voltage of 6.72 kV for a MOSFET with L gd = 40μm giving an average field strength of 1.69 MVcm -1 . The peak drain current is ~ 3 mA/mm for L g = 2μm device with a gate source separation of 3μm. The on-resistance for the device is, R on = 13 kΩ.mm, giving a power device Figure of Merit of 7.73 kWcm -2 . The R on is high due to plasma induced damage of channel and access regions. The R on and on-current density remain unchanged after passivation. The breakdown increases with L gd up to 70μm, giving a maximum breakdown voltage of 8.03 kV.