Mr. Mollo’s costumes, intricate but appearing lived-in, were based on Mr. Lucas’s instructions and on his own sketches and those of a concept artist, Ralph McQuarrie, who drew some of the earliest renderings of many of the characters.
The results included the weather-beaten martial arts outfit of Luke Skywalker, played by Mark Hamill; the monkish robes of Obi-Wan Kenobi, played by Alec Guinness; the dusty cowboy look of Han Solo, played by Harrison Ford; and the pure white dress draped over Princess Leia, played by Carrie Fisher.
For the dark side, Mr. Mollo encased the imperial storm troopers in hard white carapaces and masks and hid Darth Vader, played by David Prowse and voiced by James Earl Jones, in a swooping black cloak and a helmet that brought to mind that of a samurai. The imperial outfits were designed to embody a fascist, dehumanizing order.
Mr. Mollo said he had never expected the film to be the blockbuster it became on its release in 1977.
“Most of the crew thought that the film was a bit odd while we were making it,” he told The Times of London in 2012. “We doubted that it would ever be shown. And I remember someone asking me what I was doing and I said, ‘It’s sort of a space western and one of the heroes is a dustbin.’ ”
“Star Wars,” the surprise hit of the year, won six Oscars, including the one for Mr. Mollo’s costumes. He accepted it at the award ceremonies flanked by actors dressed as Darth Vader and storm troopers.
“As you’ve seen, the costumes in ‘Star Wars’ are really not so much costumes as a bit of plumbing and general automobile engineering,” he said in his acceptance speech.
His second Academy Award, for “Gandhi,” was shared with Bhanu Athaiya. It was one of eight won by the film, including best picture.
John Mollo was born in London on March 18, 1931. His mother, the former Ella Cockell, was an artist. His father, Eugene Mollo, escaped Russia in the 1920s and started a company built around a process for spraying cement.
Mr. Mollo traced his love of military uniforms to his watching the film “Clive of India” (1935) when he was a child and returning home from the movie theater to sketch the costume of King George II of Britain. He grew up in London and near the town of Farnham, in Surrey, and studied in a local school in Godalming before attending an art school in Farnham.
Mr. Mollo served in the King’s Shropshire Light Infantry in Hong Kong, ending his service shortly before the Korean War began.
After returning home, he helped run his father’s cement company and studied military history on the side, conferring with historians and conducting his own research. His other books include “Military Fashion” (1972) and “Uniforms of the Seven Years War” (1977, also with illustrations by Malcolm McGregor).
His first film work came by way of his brother, Andrew, who was also a military historian and film consultant. Andrew recommended him for Tony Richardson’s remake of “The Charge of the Light Brigade” (1968), set in the Crimean War. Mr. Mollo supervised the creation of about 3,000 military uniforms.
Mr. Mollo also designed costumes for science fiction films like Ridley Scott’s “Alien” (1979) and Paul W. S. Anderson’s “Event Horizon” (1997).
His first marriage, to Ann Farquharson, ended in divorce. He married Louise Pongracz in 1968. Besides her, he is survived by a son, Thomas; his brother, Andrew; and three grandchildren.
Mr. Mollo’s last work as a costume designer was on a series of television movies adapted from C. S. Forester’s novels about the Napoleonic War officer Horatio Hornblower, the last of which was shown in 2003.