NASCAR O'Reilly Auto Parts Series at Chicago Street Course

The 2026 NASCAR O'Reilly Auto Parts Series is 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 started on February 14 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.