The Xbox Series X and Series S use AMD Zen 2 CPU architecture.
Both consoles were designed around a custom AMD system-on-chip combining Zen 2 CPU cores with Radeon-based RDNA 2 graphics technology. This represented a major architectural change from the Xbox One family, whose processors were based on AMD Jaguar designs.
The Series X and Series S launched on November 10, 2020, and share the same broad CPU architecture even though they differ substantially in graphics power, memory, resolution targets, and storage. The Series X is the higher-performance model, while the Series S is a smaller digital-only console.
Zen 2 is a CPU architecture family rather than the name of the entire console chip. It should not be confused with RDNA 2, which describes the graphics architecture, or with the Xbox Series X development codename, Project Scarlett.