Apple designed the Arm-based Apple silicon chips used in modern Mac computers.
Apple silicon refers to the system-on-chip processors Apple developed for its products, including the M-series chips introduced for Macs. The transition began in 2020, when Apple announced that Macs would move away from Intel processors to chips based on the Arm architecture.
The M1 was the first Apple silicon chip used in Mac computers. Integrating the processor, graphics, memory architecture, and specialized engines into a system-on-chip design helps Apple control performance, power efficiency, and product integration.
Arm supplies the underlying instruction-set architecture, but Apple designs its own processor implementations. This distinction means Arm, Intel, and AMD are not the correct answer to a question asking who designed Apple silicon for Macs.