The 2026 NASCAR O'Reilly Auto Parts Series will be the 45th season of the NASCAR O'Reilly Auto Parts Series, a stock car racing series sanctioned by NASCAR in the United States. The season will start in mid-February with the United Rentals 300 at Daytona International Speedway and will end with the Hard Rock Bet 300 at Homestead–Miami Speedway on November 7.