Disclosed herein are systems and methods for executing multiple instruction set architectures (ISAs) on a singular processing unit. In an implementation, a processor that includes a first decoder, a second decoder, instruction fetch circuitry, and instruction dispatch circuitry is configured to execute two separate instruction set architectures. In an implementation, the instruction fetch circuitry is configured to fetch instructions from an associated memory. In an implementation the instruction dispatch circuitry is coupled to the instruction fetch circuitry, the first decoder, and the second decoder and is configured to route instructions associated with a first ISA to the first decoder, and route instructions associated with a second ISA to the second decoder.