Known as SG1, the agreement builds on a vision for regeneration developed by the council over several years and seeks to create a whole new quarter of five distinct character areas on the western side of the town centre.
The mixed-use regeneration scheme includes plans to create a series of new streets within Stevenage, as well as a redesigned, modern town square.
The development will also create new public spaces, alongside a public services hub that will bring together key council services in a single building. The hub will include a new library and health facilities, allowing residents easy access to high quality services at one location.
Work is expected to take place over several phases with the first construction project commencing in 2020.
Cllr Sharon Taylor, Leader of Stevenage Borough Council, said: “This is an exciting time for Stevenage and the future of our town centre. Signing this deal with Mace highlights our ambitions to grow our town and improve the services and amenities we currently offer to residents.
“We’ve seen a number of smaller projects already completed in our town centre as part of the regeneration programme including Market Place, Vista Tower and more, but SG1 will be one of the critical elements in driving significant, positive changes to our town.”