Opron was born in Amiens and grew up partly in French Colonial Africa, where his father's military postings took the family. A bout of tuberculosis at eighteen interrupted his early years; on recovering he enrolled at the École des Beaux-Arts in Amiens and later transferred to the École nationale supérieure des Beaux-Arts in Paris, studying architecture under Auguste Perret over eight years and also pursuing painting and sculpture.
His professional career began at Compagnie Nationale des Sucreries in 1952 before he joined the aircraft manufacturer Société Nationale de Constructions Aéronautiques du Nord in 1954, specialising in cockpit design on the Nord Noratlas. He moved to Simca in 1958, where his first major project was the 1959 Simca Chambord Présidence V8 cabriolet used by French president Charles de Gaulle. His Simca Fulgur concept of 1959 — a bubble-topped car designed for a magazine challenge to envision automobiles of the 1980s — established his reputation for forward-thinking form.
Opron joined Citroën's Bureau d'Études in 1962, reportedly after a famously adversarial first meeting with chief designer Flaminio Bertoni, who threw Opron's portfolio on the floor before hiring him. Following Bertoni's death, Opron became Responsable de Style — head of design — in 1964.
His Citroën career produced a sequence of influential models. The restyled DS received his "Nouveau Visage" front treatment for the 1968 model year, integrating four headlamps beneath glass covers that blended with the body's lines. The GS of 1970, which began as an internal competition design that beat a submission from Giorgetto Giugiaro, brought aerodynamic efficiency to the mid-range segment. The SM of 1970 — originally intended as a Le Mans racer before evolving into a grand touring car — is the model most closely associated with Opron's name and exemplifies his approach of creating form that appears to move even at rest.
His personal favourite project at Citroën was the CX of 1974, which debuted as the successor to the DS and extended the same aerodynamic logic into a modern, wedge-shaped form. When Citroën declared bankruptcy in 1974 and was merged with Peugeot, Opron departed.
In 1975 Opron joined Renault, where he led the redesign of the Alpine A310 to accommodate the V6 PRV engine and address aerodynamic shortcomings of the original shape. His most commercially significant Renault designs were the Fuego sports coupé of 1980 and the Renault 9 and 11 models, the latter pair adapted for the American market as the Alliance and Encore in collaboration with AMC's Dick Teague. He also participated in the Renault AE Magnum truck line, released in 1990 and named European Truck of the Year. Opron left Renault in 1985.
At Fiat's Centro Stile, Opron led advanced studies and produced the earliest sketches for a project designated ES 30 — Experimental Sportscar 3.0 litres — that was fully developed by Antonio Castellana and debuted at the 1989 Geneva Motor Show as the highly controversial Alfa Romeo SZ coupé, nicknamed "Il Mostro." He reached mandatory retirement age at Fiat in 1992.
From 1991 to 2000 Opron operated an independent design consultancy in Verrières-le-Buisson, south of Paris. Among his clients was Ligier, the microcar manufacturer, for whom he designed the original Dué that debuted at the 1998 Paris Motor Show.
Opron was nominated for the 1999 Car Designer of the Century competition alongside twenty-four other designers. He received Car Design News' Lifetime Achievement Award in 2016. A celebration of his career, OPRON 50 Years of Style, was held on 11 May 2002. He died on 29 March 2021 in Antony, near Paris, from complications of COVID-19 at the age of 89.