Windows 11 Pro supports a maximum of 2 physical processors. This means two separate CPU packages or sockets, not two processor cores or two logical threads.
The distinction matters because modern CPUs contain many cores, and technologies such as simultaneous multithreading can make one physical processor appear as multiple logical processors. Windows 11 Pro supports substantially more than two cores; the limit concerns physical CPU packages.
Windows editions have different hardware ceilings. Windows 11 Home supports one physical processor, while Pro supports two. Windows 11 Pro for Workstations is aimed at higher-end systems and supports up to four physical processors.
This limit is why dual-socket workstations commonly require Windows Pro rather than Home. A single high-core-count processor is still one physical processor, so it does not use up the two-CPU allowance merely because it has dozens of cores.