The film was released in Melbourne on Boxing Day 1906 and played to standing-room-only crowds, according to National Film and Sound Archive senior curator Gayle Lake.
"It's thought to be the world's first feature-length narrative film, so it's very significant in the history of Australian cinema," she told AAP.
The film depicts the story of fugitive killer Ned Kelly as he is hunted by police in the Victorian bush, culminating in the bushranger confronting the officers in his improvised suit of armour.
It's believed the silent film was originally shown with actors providing dialogue from behind the screen along with sound effects such as gunshots.
However all of the Kelly Gang prints had vanished by the end of World War II and the film was considered lost.
Fragments began to resurface in 1976, with some scraps uncovered in old collections and others found on a rubbish tip.
The film archive restored the remnants for the movie's centenary in 2006.
"We had our researchers and curators try and piece together where these actual clips were situated within the film, in terms of its narrative ... it was painstaking activity to actually put it all together," Ms Lake said.
While the film lasted more than an hour when it was first released, the restored footage runs for 17 minutes.
The quality of the fragment has been improved during the restoration process, with the jumpiness of old reels gone and dirt and scratches removed.
A few scenes that were printed in reverse, making the gun-toting actors appear left-handed, have been flipped around the right way.
Archive research into the Kelly Gang film also reveals much about the mechanics of early filmmaking.
The film's budget was 1000 pounds - a substantial investment for the time and worth around $158,000 in today's money - with profits reportedly amounting to 25 times that figure.
Actors were paid one pound a day and production spanned six months.
The film was shot in a linear timeline with one camera, which was mostly set to a wide frame to match the theatre productions audiences were then used to.
Much of the film is believed to have been shot on the Charterisville Estate, near what is now the Melbourne suburb of Heidelberg.
The archive says reports of crime followed the initial screenings, with one group of children in Ballarat breaking into a photo studio before bailing up another group of kids.
The film was banned in the "Kelly country" towns of Benalla and Wangaratta.
The Story of the Kelly Gang screens with the short film Your House and Mine and the feature The Rise and Fall of Squizzy Taylor on August 14.
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