As per the reports, Manuel Pellegrini wants to improve his defensive unit and he has identified the Swansea duo as targets.
Mawson had a fantastic season last year and he will be a very good addition to West Ham if they can pull it off.
The report claims that West Ham have been locked in talks with Swansea regarding the defender and an agreement is close to being reached.
The Hammers will pay around £20m for the 24-year-old defender.
Meanwhile, Fabianski will be brought in as a replacement for Joe Hart. The Swansea keeper has been one of the best shot-stoppers in the country for a while now and he would be a solid addition.
Fabianski is valued at around £9m but West Ham are confident of agreeing a deal worth around £7m.
Pellegrini will want to break into the top half next season and signings like Mawson and Fabianski would certainly help him achieve his objectives.