Donald N. Frey, the engineer who spearheaded the design and development of the Mustang, the spunky, stylish, affordably priced “pony car” that the Ford Motor Company rolled out in the mid-1960s in one of the most successful car introductions in automotive history, died March 5 in Evanston, Ill., where he lived. He was 86.

The cause was a stroke, his son Christopher said.

Though much of the Mustang was borrowed from other Ford vehicles, including a Falcon chassis, the car developed an identity all its own for a younger generation in search of new looks and experiences. It was designed to appeal to both men and women, had a dash of elegance copied from European sports cars, and featured a galloping steed in the middle of its grille that buyers thought was, well, really cool.

Steve McQueen was almost upstaged by the souped-up Mustang he drove in the movie “Bullitt.”

Mr. Frey and his team created the car — from approval by top management to the showroom — in just 18 months, and expectations were modest when it was introduced on April 17, 1964, at the New York World’s Fair. Ford figured it would sell 80,000 Mustangs in its first year. It sold more than a million in its first two years.

Mr. Frey (pronounced fry) would go on to other achievements. He was chairman and chief executive of the Bell & Howell Company, recipient of the National Medal of Technology and a member of the executive board of the World Bank. He was proudest, he said, of helping to introduce safety improvements like disc brakes and radial tires to Ford cars.