The development will be The Guinness Partnership’s biggest single consented residential scheme in its 129-year existence.
North West developer X1 Developments sold the Hunslet Road near Leeds Docks and the Royal Armouries Museum to the housing association.
The affordable housing element will now be upped from 5% to 35%.
The deal was supported with cash from a £224m Homes England grant to a strategic partnership of Guinness and Stonewater housing associations to start building an extra 4,500 affordable homes across England by 2022.
Catriona Simons, chief executive of The Guinness Partnership, said: “This site, within the Leeds South Bank Regeneration and Innovation District, is a fantastic opportunity for us to create over 900 homes in a vibrant new neighbourhood in Leeds. We intend at least 35% of the homes to be affordable.
“We plan to build over 9,000 new homes by 2023, with our vision to create great homes where people are proud to live. Funding from Homes England means we have been able to extend our development programme in Leeds to fulfil that vision.’’
Councillor Richard Lewis, Leeds City Council’s executive member for regeneration, transport and planning, said: “The Guinness Partnership’s proposals are fantastic news for Leeds.
“That it is committing to its biggest ever scheme here and intending to deliver so many new affordable homes is a real mark of confidence in our vision for the South Bank, where we want to ensure regeneration and growth benefits all the city’s residents.”