The Gym Group, owned by private investment company Bridges Ventures, has opened a 24-hour gym in Liverpool One.
The facility occupies 19,500 sq ft over three floors in the tallest building in Grosvenor's 42-acre scheme.
The company's second North West gym, and fifth in total, will open in November in Bruntwood's City Tower, central Manchester. The Gym also operates in Guildford, Hounslow and Vauxhall, London.
Guy Butler, projects director at Grosvenor, said: "The opening of the city's first 24 hour gym is a significant indicator of how far Liverpool has come. Cities such as London and New York are renowned for their 24-hour culture and it is an encouraging sign to see this arriving in Liverpool.
"Gone are the days when buildings were developed in isolation, residents expect a certain amount of infrastructure and lifestyle facilities, such as this, right on their doorstep."