The 2021 NASCAR Xfinity Series was the 40th season of the NASCAR Xfinity Series, a stock car racing series sanctioned by NASCAR in the United States. The season began at Daytona International Speedway with the Beef. It's What's for Dinner. 300 on February 13. The regular season ended with the Food City 300 at Bristol Motor Speedway on September 17. The NASCAR playoffs ended with the NASCAR Xfinity Series Championship Race at Phoenix Raceway on November 6.

Following the Food City 300 at Bristol Motor Speedway, A. J. Allmendinger of Kaulig Racing clinched the Regular Season Championship. Chevrolet took the Manufacturer Championship following the Dead On Tools 250 at Martinsville Speedway. At the season finale, Daniel Hemric of Joe Gibbs Racing scored his first career win and claimed the Xfinity Series championship. It was also the first Xfinity Series championship for the Toyota Supra.

Daytona, Phoenix, Texas, and Circuit of the Americas revealed their race dates ahead of the release of the entire schedule, which NASCAR announced on October 30, 2020.

Note: The Dash 4 Cash races (the spring races at Martinsville, Talladega, Darlington and Dover) are listed in bold.

(key) Bold – Pole position awarded by time. Italics – Pole position set by competition-based formula. * – Most laps led. ¹ – Stage 1 winner. ² – Stage 2 winner ^1–10 – Regular season top 10 finishers.
. – Eliminated after Round of 12 . – Eliminated after Round of 8

(key) Bold – Pole position awarded by time. Italics – Pole position set by competition-based formula. * – Most laps led. ¹ – Stage 1 winner. ² – Stage 2 winner ^1–10 – Regular season top 10 finishers.
. – Eliminated after Round of 12 . – Eliminated after Round of 8

NOTE: The No. 54 Joe Gibbs Racing Toyota used an ineligible driver in selected races and could not acquire bonus points for those races.