AbstractGate controllability is a key factor that determines the performance of GaN high electron mobility transistors (HEMTs). However, at the traditional metal‐GaN interface, direct chemical interaction between metal and GaN can result in fixed charges and traps, which can significantly deteriorate the gate controllability. In this study, Ti₃C₂T_x MXene films are integrated into GaN HEMTs as the gate contact, wherein van der Waals heterojunctions are formed between MXene films and GaN without direct chemical bonding. The GaN HEMTs with enhanced gate controllability exhibit an extremely low off‐state current (I_OFF) of 10⁻⁷ mA mm⁻¹, a record high I_ON/I_OFF current ratio of ≈10¹³ (which is six orders of magnitude higher than conventional Ni/Au contact), a high off‐state drain breakdown voltage of 1085 V, and a near‐ideal subthreshold swing of 61 mV dec⁻¹. This work shows the great potential of MXene films as gate electrodes in wide‐bandgap semiconductor devices.