Regazzoni drove for Ferrari from 1970-72 and 1974-76, winning the Italian Grand Prix in 1970 and 1975, the German GP in 1974, and the United States GP in 1976. In 1974 he was second to Emerson Fittipaldi in the F1 championship. Regazzoni also raced for BRM, Ensign, Shadow and Williams, with whom he won the British GP at Silverstone in 1979. Regazzoni was confined to a wheelchair in 1980 when he suffered spinal damage in a crash during the US Grand Prix West in Long Beach, California.
Born Gianclaudio Regazzoni, he was raised in Ticino, Switzerland's predominantly Italian-speaking area bordering Italy. He was effectively considered to be an Italian by Italians, which was a point of great pride during his years with Ferrari, however, he holds a Swiss passport and official Formula One records register his as Swiss.
During the late 1960s he raced in F3 and F2. He was certainly a rough and ready competitor who got involved in more than his fair share of accidents. In 1968 he was implicated in the fatal accident involving Englishman Chris Lambert's Brabham after a collision with his Tecno during the Dutch round of the European F2 Trophy at Zandvoort. He was subsequently exonerated but many people thought this incident would blight his career progress. Howver it did not prevent him from graduating into F1 as an occasional member of the Ferrari F1 team in 1970.
Regazzoni's first victory came during his first season in Formula 1, when he won the Italian Grand Prix at Monza. Although he only competed in eight of the 13 races, he finished third in the championship, behind team-mate Jacky Ickx and the late Jochen Rindt, who posthumously won the world championship.
His victory in the Italian Grand Prix at Monza cemented his position as regular team-mate to Jacky Ickx for the next couple of seasons. His tough uncompromising style followed him into Formula 1, barging Jackie Stewart's Tyrrell off the road in the 1972 German Grand Prix at Nurburgring. It was one of the few occasions in which Jackie has appeared genuinely aggrieved by the performance of a rival, but "Regga" just seemed to shrug it aside.
At the end of the 1972 season he left Ferrari for BRM where he teamed-up with Jean Pierre Beltoise and Niki Lauda. But, after a barren season in 1973, he returned to Ferrari in 1974 and suggested to Enzo Ferrari to hire Niki Lauda as well. Between them and with team manager Luca Cordero di Montezemolo and technical director Mauro Forghieri, they won 15 Grand Prix, two constructors titles, and one drivers championship (Lauda in 1975) for Ferrari.
Regazzoni's best season was 1974, when he lost the championship to Emerson Fittipaldi by only three points. The following year he won at Monza and in 1976 he won the first Long Beach Grand Prix in the Ferrari 312T.
At the end of 1976 season he was replaced at Ferrari by Carlos Reutemann and found a berth with Ensign for 1977. Regazzoni's desire to drive in F1 meant that he didn't mind driving for a small constructor. He finished fifth at Monza and Watkins Glen with these results proving almost as enjoyable as victory at the wheel of a Ferrari.
In 1978 he joined the Shadow F1 outfit but with little to write home about. Fortunately he was then hired by Frank Williams to partner Alan Jones in 1979. Regazzoni paid him back by giving the team its maiden win at Silverstone, but he was replaced by Carlos Reutemann at the end of the season.
In the latter part of the 1970s Regazzoni also drove in the Indy 500 for McLaren.
After being replace at Williams, Regazzoni went back to Ensign but in the 1980 Long Beach race the brake pedal snapped at the end of a long high-speed straight. and Regazzoni's crashed at unabated speed into a Brabham that had already retired and was parked in the escape road around a corner. In the crash Regazzoni sustained back injuries which left him paralyzed from the waist down. He became very active in helping disabled people get equal opportunities.
Despite being confined to a wheelchair Clay continued to race in the Paris-Dakar Rally and in sportscar events with hand-controlled machinery. In 1996 he was refused an FIA international license to race in the World Sportscar Championship.
Regazzoni shared his time between Monaco and Lugano, and did the occasional TV commentaries for Swiss and Italian television.
Regazzoni was killed when his Chrysler Voyager arrived at high speed at a sudden and unexpected traffic jam on the A1 Milan-Bologna motorway just west of Parma. He was in collision with a truck, there were no other victims.
The subsequent autopsy did not reveal any fatal injuries resulting from the crash which would suggest that the 67-year-old died of natural causes either before the accident or in its immediate aftermath.