The race distance was reduced from 32 to 28 laps for the 1966 edition. The event was defined by a severe rainstorm that struck the circuit during the opening lap, causing a heavy wall of rain at the Burnenville corner. This weather decimated the field immediately; more than half of the competitors crashed out on the first lap, leaving only seven runners to begin the second lap.
Several drivers went off at Burnenville, including Jo Bonnier, whose Cooper T81 came to rest balanced on a parapet with its front half suspended in the air. At the Masta Kink, Jackie Stewart crashed his BRM P261 into a telephone pole and landed in a ditch. Stewart remained trapped upside down in the car for 25 minutes, submerged to his waist in fuel. He was eventually rescued by fellow drivers Graham Hill and Bob Bondurant, who had also gone off near the site and utilized a toolkit borrowed from a spectator to free him. Jack Brabham also lost control of his Brabham BT19 at the Masta Kink at 135 mph but was able to regain control and continue the race. Jim Clark was forced to retire on the first lap when floodwater entered the Climax engine of his Lotus 33.
Following the attrition of the first lap, John Surtees secured the win with a 42-second lead over Jochen Rindt. Driving a Cooper T81, Rindt earned his first podium finish, which also marked the first podium for the Cooper-Maserati partnership. Lorenzo Bandini finished third in a Ferrari 246.
The crash involving Jackie Stewart at the Masta Kink became a pivotal moment in the sport's history. Following his experience of being trapped in a fuel-soaked car with no immediate professional rescue, Stewart began a campaign for improved racing safety. These efforts continued for decades and intensified as his influence grew over the subsequent seven seasons of his competitive career.
The race also marked the Formula One World Championship debut for two entities: the American constructor Eagle and the Italian engine supplier Serenissima. Additionally, the event was the 100th World Championship race to feature a French participant.
The 1966 Belgian Grand Prix was used as a primary filming location for the motion picture Grand Prix. An eight-minute segment of the film utilizes a mix of live race footage and staged scenes. During the actual race, John Surtees doubled for the fictional character Jean-Pierre Sarti, while Lorenzo Bandini doubled for Nino Barlini. Because Jackie Stewart was doubling for the character Scott Stoddard—who was scripted to be recovering from a crash at that point in the film—the production avoided filming him in action, a task made simpler by his early retirement from the race.
To accommodate the film's requirements following the withdrawal of the McLaren team, Bob Bondurant's car was repainted white overnight to represent the fictional "Yamura" brand. James Garner’s white Yamura seen in the film did not participate in the actual Grand Prix. Additionally, Phil Hill completed one lap of the circuit with a camera mounted to the nose of his car; by avoiding the first-lap accidents, he was able to capture footage of the wreckage.
The results at Spa-Francorchamps significantly altered the early 1966 championship standings. With his third-place finish, Lorenzo Bandini took the lead in the World Championship of Drivers by a point over both John Surtees and Jackie Stewart.
The victory was Ferrari's fifth win at the Belgian Grand Prix during the World Championship era. By the conclusion of the event, the Scuderia had amassed a total of 17 podiums, 5 pole positions, 5 fastest laps, and 2 Grand Slams at the Spa-Francorchamps circuit. For the Cooper Car Company, the race validated their move to the three-litre Maserati V12 sports car engine, which had been adopted to meet the new technical regulations of the 1966 season.