The Sunday People will drop the "Sunday from its masthead from this Sunday and revert to The People. It is launching The SP, a 48-page sports paper, as part of its package.
Trinity Mirror is spending £2 million on the relaunch, which includes a revamp of the main paper with features and showbiz elements. The People magazine has also been redesigned.
Neil Wallis, the editor of The People, said: "This was a major decision, particularly when you look at how tough the market is. We have had these plans for some time but Trinity Mirror has focused, rightly, on The Mirror's rebrand. The Sunday Star has probably encouraged us to bring our plans forward but we are doing what we believe is right for the paper."
Wallis hopes that the revamp will increase The People's existing circulation of 1.3 million.
M&C Saatchi has developed a launch campaign for The People to support the debut of the sports paper, edited by Lee Clayton, The People's sports editor.