The practice, which won an RIBA award last year for its £200m British Airways business centre at Heathrow Airport, is designing the 6000 m2 speculative office building in Lanyon Place. The ground floor will include space for a public gallery.
The Lanyon Place development already includes the Belfast Hilton and BT's Northern Ireland headquarters.
Niels Torp, which has been keen to win more work in the UK, beat off a shortlist including German practice Behnisch, Behnisch & Partner, Danish architect Henning Larsens and Henke & Schreieck from Austria.
Niels Torp project leader Harald Lone said the scheme had been a particularly unusual one for the practice: "We felt the site was very special. It's not like anything we've done before.
"A lot of people have come to us and said they had never seen an office block like this before. Our response is, neither have we." Lone said the neighbouring buildings, such as Waterfront Hall, had influenced the firm's design, which is called "The Soloist".
A lot of people said they had never seen an office block like this before
Harald Lone, Niels Torp
He said: "We wanted a building that will look small under a big roof. It's like a pavilion or sculpture set against the bigger buildings.
"Our design complements the Waterfront Hall through its airy expression, opening up sight lines right through the building." One idea behind the building was to enable people to see the Waterfront Hall through the new building's glazed structure.
Lone added: "The free arrangement of fan-shaped forms, gathered under an exciting, slender roof canopy, make a valuable counterpoint to the monumental, cylindrical volume of the Waterfront Hall." The competition was run by the Royal Society of Ulster Architects for Lanyon Place developer Dunloe Ewart and Belfast's Laganside Corporation.
Dunloe Ewart chief executive Barry Gilligan said: "The superb design brings the regeneration of Belfast into its next and best phase." Construction is due to start on the project by the end of the year, once another speculative office development, 9 Lanyon Place, is completed.
Gilligan said he was confident that Dunloe would find tenants for the site well before construction was complete, due for the end of 2001.