The firm will break ground in the coming weeks on the site of the former Oceana nightclub at 71/72 The Kingsway.
Set for completion in the summer of 2023, the five-storey development will include 114,000 sq ft of commercial floorspace.
The developments will include two underground levels with new links between The Kingsway and Oxford Street.
John Boughton, regional managing director of Bouygues UK, said: “To work on such an innovative and environmentally-friendly building is going to be really rewarding for our team and we can’t wait to break ground and get going.”
The 71/72 Kingsway development is being funded by Swansea Council and the Swansea Bay City Deal. It is also supported by the European Regional Development Fund through the Welsh Government.