The National Magazine company and Hachette Filipacchie are to merge and become known as Hearst Magazines UK.
The move follows the news which broke in March that NatMag owner Hearst had bought the French media group Lagardere, which owns Hachette Filipacchi, in a £574m deal.
According to Hearst UK - the combined group will reach 33 per cent of UK adults and 47 per cent of UK women with 26 magazines and 22 digital titles.
Former NatMag chief executive Arnaud de Puyfontaine has been made chief executive of Hearst Magazines UK.
He said: 'This move consolidates our status as a leading UK media owner. NatMag and Hachette Filipacchi have built a stable of world-class brands and this combined portfolio gives us a unique opportunity to develop and expand our commercial potential. We very much look forward to working with our new colleagues on this exciting venture."
Hachette Filipacchi had a combined magazine circulation in the UK in the second half of December 2010 of 887,009. Its main titles were: All About Soap, Elle, Elle Decoration, Inside Soap, Psychologies Magazine and Red.
NatMag had a combined magazine circulation of 3,112,939 in the second half of 2010. Its titles include: Best, Company, Cosmopolitan, Country Living, Esquire, Good Housekeeping, Harpers Bazaar, Prima, Real People, Reveal, She and Zest.