It may look low-key, but the 2021 Audi S3 is anything but tame under the hood. With sharp handling and turbocharged punch, this is subtle performance at its finest. Blink and you’ll miss it—literally.

We recently had the opportunity to jump behind the wheel of both the regular A3 and its high-performance S3 sibling around Denver, Colorado, to see what the fuss is all about and share our first ...