The selection is likely to cause much disagreement, omitting recognised classics such as 'Bladerunner', 'Star Wars' and 'Citizen Kane'.
The list has been voted for by a panel of film experts including Lord David Puttnam, film critics Jason Solomons and Karen Krizanovich, Channel 4 head of film and drama Tessa Ross and the film director Menhaj Huda.
Channel 4 says each film has been chosen for its unique and creative approach to filmmaking. The season begins at 9pm on Sunday 23rd July with the showing of Sofia Coppola's Oscar-winning 'Lost in Translation', starring Bill Murray and Scarlett Johansson, and the FilmFour production, 'Sexy Beast'.
The relaunch, that sees the name change to Film4, is being backed by an ad campaign starting this week. It includes ads featuring Dame Judy Dench and Ewan MacGregor, dressed as a lobster and a tomato in Trafalgar Square handing out cheap looking "FilmFour is free" leaflets. In another ad Rhys Ifans going door-to-door canvassing viewers on a suburban housing estate, and explaining to an elderly lady over a cup of tea that Film Four is free.
Andy Duncan, Channel 4 chief executive, said: "FilmFour has always been about great films you know and great films you don't - now all those great films will be absolutely free."
FilmFour was launched on 1st November 1998 and was available on a subscription-only basis in digital cable and satellite homes and currently has over 300,000 subscribers, each paying up to £7 a month to receive the service. The final day of paid-for transmission will be July 19.
The new free-to-air Film4 will screen six films a day, with a new film starting approximately every two hours between 3pm and 3am.
Classic films will be shown earlier in the day with modern Hollywood output and US and UK independent cinema at peak time. Foreign language and cult cinema will be shown late at night.
The channel will also premiere key titles financed and co-produced by Channel 4's film division Film Four Productions.
Channel 4 is also planning the launch of a Film4 branded video-on-demand subscription service on various media platforms - including broadband, mobile and cable - to follow later in the year.
The 50 films list's final order will be revealed in a programme on July 22, which will also feature behind-the-scenes insights and interview the films' actors and directors including Quentin Tarantino, Mike Leigh, Sir Ben Kingsley, Steven Spielberg, Liza Minnelli, Samuel L Jackson and Jonathan Pryce.
The full list:
2001 - A Space Odyssey
A Bout De Souffle
Aguirre, The Wrath of God
All About Eve
Boyz N the Hood
Breakfast Club, The
City of God
Come and See
Dawn of the Dead
Fanny and Alexander
The Ipcress File
King of Comedy, The
Lagaan: Once Upon a Time in India
Lost in Translation
Night at the Opera
North by Northwest
The Royal Tenenbaums
Secrets and Lies
The Shawshank Redemption
Terminator 2: Judgement Day
This Sporting Life
Three Colours Trilogy
Touch of Evil
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the Forum.