TSMC is the world’s largest contract chipmaker by revenue and manufactures processors for Apple.
TSMC operates as a semiconductor foundry, meaning customers provide chip designs and TSMC produces them in its fabrication plants. Apple designs its own processors, including chips in the A-series used in iPhones and the M-series used in Macs, while TSMC manufactures many of those chips.
This division of labor is central to the modern semiconductor industry. A company can specialize in architecture and product design without owning the factories needed to make advanced processors. TSMC’s customers include many major technology companies, and its manufacturing technologies are used in processors for mobile devices, personal computers, servers, and artificial-intelligence systems.
The answer is not Apple because Apple designs products and chips but is not primarily a merchant semiconductor foundry. It is also not Samsung Electronics, which both designs products and operates its own foundry business.