PureGym plans to open its new facility off Seaforth Road in the West Dunbartonshire town.
No firm opening date has yet been announced, but the company says the gym will open in "early 2014" in a site that spreads over 16,009 sq ft.
PureGym, which has a facility in Bath Street in Glasgow city centre, and 60 around the UK, is promising new members "access to a vibrant and spacious gym 24 hours a day, seven days a week."
It will be filled with more than 220 pieces of the latest gym equipment to cover training requirements for anyone, regardless of their level of fitness.
The gym will also offer more than 40 free classes every week plus additional specialist classes such as Zumba and the new South African dance class, Bokwa. There are also plans to open a branch in Paisley.