The money will be used to create a new shopping centre, offices, homes, bars and restaurants and a hotel. A 650-space car park is also set to be created.
Kirklees Council said the investment will "kickstart and trigger the redevelopment of the town".
Compulsory purchase powers may be used to help developers secure the site, which takes in Halifax Road, Northgate, Bond Street, Branch Road, Westgate, Grove Street, Daisy Hill, Church Street, South Street and the bus station.
Council leader Robert Light said: "The scale of this scheme is immense, and coupled with all the other things in the pipeline for the town and surrounding areas. It will change the face of Dewsbury to the benefit of tens of thousands of people for generations to come."