The 6501 is an eight-bit microprocessor, the first sold by MOS Technology. The 6501 is pin-compatible with the Motorola 6800 and is the first member of the 65xx series of microprocessors.

The 6502 is a 6501 with the pins re-arranged following a lawsuit by Motorola over the 6501's pin arrangement. The 6502 also added a two-phase clock generator, so it only needed a single phase clock input, simplifying system design. See the 6502 article for further details.

MOS Technology 6501