History enthusiasts will now be able to watch footage of everything from the coronation of Queen Elizabeth II, the Hiroshima bombing, and Emily Davison throwing herself under the King's horse, in high resolution.
Alastair White, general manager of British Pathe, described the archive as a "treasure trove".
"Our hope is that everyone, everywhere who has a computer will see these films and enjoy them," said Mr White.
"This archive is a treasure trove unrivalled in historical and cultural significance that should never be forgotten. Uploading the films to YouTube seemed like the best way to make sure of that."
Considered to be the finest newsreel archive in existence, British Pathe was once a dominant feature of the British cinema experience.
Spanning from 1896 to 1976, the collection includes footage from Britain and around the world of major events, famous faces, fashion trends, travel, sport and culture.
The project is being managed by German company Mediakraft, which has been responsible for numerous past YouTube successes. The company will be creating new content using British Pathe material in English and in foreign languages.
The newsreel's 3,500 hours of footage was first digitised in 2002 thanks in part to a grant from the National Lottery.