Stansted’s owner Manchester Airports Group (MAG) said in a statement that the building will include larger immigration and baggage reclaim areas.
Work is expected to take up to three years to complete, and will begin in late 2018.
The existing departures building will be reconfigured to provide more space at check-in and in security.
The new building, designed by Pascall & Watson Architects, has been granted planning permission by Uttlesford District Council.
The airport’s Chief Executive Andrew Cowan said the site would “transform our infrastructure and facilities to give our passengers the best possible experience”.
“Stansted is a national asset and our investment will continue to boost competition and support economic growth, jobs and international connectivity for London and the East of England,” he said.
“At a time when airport capacity in the country is at a premium, Stansted is playing a vital role in supporting both the regional and national economy. This project will strengthen our ability to do this by enabling us to make the most efficient use of our single runway.”