Notting Hill Housing and Genesis Housing Association have agreed in principle to merge.
The boards of both organisations agreed the merger proposal on Wednesday 19 July 2017.
The new organisation, Notting Hill Genesis, will have 54,000 homes across London and 64,000 across London and the South East, half of which will be general needs homes with social or affordable rents.
The new organisation will serve a total of 170,000 residents and be the largest provider of shared ownership tenure in the country.
The merger will be complete in early 2018.