The 2018 Auto Club 400 was a Monster Energy NASCAR Cup Series race that was held on March 18, 2018, at Auto Club Speedway in Fontana, California. Contested over 200 laps on the two-mile (3.2 km) D-shaped oval, it was the fifth race of the 2018 Monster Energy NASCAR Cup Series season.

Auto Club Speedway (previously California Speedway) was a two-mile (3.2 km), low-banked, D-shaped oval superspeedway in Fontana, California which hosted NASCAR racing annually from 1997 to 2023. It was also used for open wheel racing events. The racetrack was located near the former locations of Ontario Motor Speedway and Riverside International Raceway. The track was owned and operated by International Speedway Corporation and was the only track owned by ISC to have its naming rights sold. The speedway was served by the nearby Interstate 10 and Interstate 15 freeways as well as a Metrolink station located behind the backstretch.

Kevin Harvick was the fastest in the first practice session with a time of 38.082 seconds and a speed of 189.066 mph (304.272 km/h).

Martin Truex Jr. scored the pole for the race with a time of 38.592 and a speed of 186.567 mph (300.250 km/h).

Kevin Harvick was the fastest in the second practice session with a time of 38.694 seconds and a speed of 186.075 mph (299.459 km/h).

Kyle Busch was the fastest in the final practice session with a time of 38.779 seconds and a speed of 185.668 mph (298.804 km/h).

Stage 1 Laps: 60

Stage 2 Laps: 60