The 1986 Budweiser 400 was the 12th stock car race of the 1986 NASCAR Winston Cup Series, the second race of the 1986 NASCAR Winston West Series, and the 18th iteration of the event. The race was held on Sunday, June 1, 1986, before an audience of 45,126 in Riverside, California, at the short layout of Riverside International Raceway, a 2.62 miles (4.22 km) permanent road course layout at the track. The race took the scheduled 95 laps to complete.

With two laps left in the race, a caution flag was called for a four car wreck. The top two at the time, Hendrick Motorsports' Tim Richmond and Junior Johnson & Associates' Darrell Waltrip, raced back to the line, with the driver leading by the start of the next lap essentially being guaranteed the victory. In the final turn of the track, Waltrip was able to pass Richmond exiting the turn, giving Waltrip the lead and the victory. The victory was Waltrip's 68th career NASCAR Winston Cup Series victory and his first victory of the season. To fill out the top three, Bud Moore Engineering's Ricky Rudd finished third.^[1][2]

Riverside International Raceway (sometimes known as Riverside, RIR, or Riverside Raceway) was a motorsports race track and road course established in the Edgemont area of Riverside County, California, just east of the city limits of Riverside and 50 mi (80 km) east of Los Angeles, in 1957. In 1984, the raceway became part of the newly incorporated city of Moreno Valley. Riverside was noted for its hot, dusty environment and for being somewhat of a complicated and dangerous track for drivers. It was also considered one of the finest tracks in the United States.

Qualifying was split into two rounds. The first round was held on Friday, May 30, at 6:30 PM EST. Each driver had one lap to set a time. During the first round, the top 20 drivers in the round were guaranteed a starting spot in the race.^[3] If a driver was not able to guarantee a spot in the first round, they had the option to scrub their time from the first round and try and run a faster lap time in a second round qualifying run, held on Saturday, May 31, at 2:30 PM EST. As with the first round, each driver had one lap to set a time. For this specific race, positions 21-40 were decided on time, and depending on who needed it, a select amount of positions were given to cars who had not otherwise qualified but were high enough in owner's points; up to two provisionals were given.^[4]

Darrell Waltrip, driving for Junior Johnson & Associates, won the pole, setting a time of 1:20.611 and an average speed of 117.006 miles per hour (188.303 km/h) in the first round.^[5]

No drivers failed to qualify.