Apparatus and methods for radio frequency (RF) switches are provided herein. In certain implementations, an RF switching circuit includes an adaptive switch bias circuit that controls gate and/or channel voltages of one or more field effect transistor (FET) switches. Additionally, the adaptive switch bias circuit is powered by a power high supply voltage and a power low supply voltage, and can be used to selectively turn on or off the FET switches based on a state of one or more switch enable signals. The adaptive switch bias circuit adaptively biases that gate and/or channel voltages of the FET switches based on a voltage difference between the power high and power low supply voltages to provide switch biasing suitable for use with two or more different power supply voltage levels.