Julius Hagen (1884–1940) was a German-born British film producer who produced more than a hundred films in Britain.

Hagen originally worked as a salesman for Ruffels Pictures. He then worked his way up to become a production manager in the British silent film industry before becoming an independent producer in 1927. From 1928, he took control of Twickenham Studios and became one of the most prolific and successful producers of Quota quickies. He later switched to making more prestigious films, but in 1937 he was forced into bankruptcy and lost control of Twickenham.

Hagen also directed a film, the 1928 adaptation of an Agatha Christie novel The Passing of Mr. Quinn.

Hagen was born in Hamburg but emigrated to Britain when he was still a child. He began his entertainment career as a stage actor, but in 1913 moved into the film industry and worked for several years as a film salesman. By 1917, he was a partner in a film distribution company, but this went bankrupt in 1919.

For the next few years, Hagen returned to selling films around the country and built up a reputation as an effective salesmen, enjoying success with films that were considered difficult to sell. He was then given a job as production manager with Stoll Pictures, one of the leading British Studios, whose main studio was based in Cricklewood. Following the Slump of 1924, the number of films produced rapidly declined and, in 1926, Hagen lost his job. He then moved to the rival company Astra-National where he co-produced The Flag Lieutenant, one of the biggest hits of 1926, starring Henry Edwards.

In 1927, Hagen and Edwards formed a separate production company, and created a sequel The Further Adventures of the Flag Lieutenant, which also proved popular with British audiences. The film was made at Twickenham Studios in Middlesex, and Hagen used it as his primary base of operations thereafter. Hagen followed this with The Fake (1927). He tried to secure financial backing for further films from the City of London, but after a brief boom in the late 1920s it was increasingly difficult to secure backing there for film production.

In 1927, following the Slump of 1924 and the rapid drop in British film production, the British Parliament passed the Cinematograph Films Act which was designed to protect British filmmaking from foreign competition. It imposed a quota for distributors and exhibitors, who had to show a fixed minimum percentage of British films each year. It meant that cinemas now required an urgent increase in the availability of British films and began by producing The Passing of Mr. Quin, an Agatha Christie adaptation, which he directed himself.

Hagen gradually began to gain commissions from British distributors who needed cheap films to help them comply with the quota. He founded the Strand Film Company in 1928 and in December that year secured the lease on Twickenham Studios. Working from Twickenham, Hagen soon established a stock company of actors and technicians to work on his films. He kept an eye to the international market, and imported overseas stars such as Margot Landa to appear in his films. He also arranged for co-productions including the Anglo-French At the Villa Rose. The sudden arrival of sound created an increased demand for double bills and it soon became established that the low-budget films would be screened as a prelude to the more expensive main features produced by major studios. They were commonly labelled "Quota Quickies", and can be considered equivalent to the B movie.