The Real Gym on Ormskirk Road has confirmed that it has closed for business and will no longer be operating.
The gym said that members will be able to register to use facilities at nearby JD Gyms on Market Street.
Users were told membership would be free for the first two months, after which they would have to pay.
Representatives for the gym told customers about the closure via an email on Tuesday and later confirmed the news on their Facebook page in post on Wednesday, April 11.
In a statement posted to their Facebook page a spokesman for the gym said: "To all our fantastic members I’m afraid the closure of Real Gym Preston is correct.
"We again thank you for all your support.
"Please follow the instructions on your emails to activate your membership at JD Gyms Preston."
Preston City Centre BID Manager Mark Whittle said: "It’s disappointing when any business closes and we wish the staff well with future endeavours.
"Personal fitness is a busy market place and the demands of sector customers continues to evolve.
"Preston continues to out-perform many of the region’s towns and cities in relation to business openings and closures, but we must all support our local businesses to ensure the economic success of our city."
Classes were still being advertised on the gym's social media pages on Monday, and the news has come as a shock to its loyal followers.
One user said: "Absolutely gutted, only gym I've enjoyed going to and felt comfortable."
Another said: "Only gym I ever felt comfortable in. Was going to re-join after exams but now I can't."
Representatives for Real Gym, JD Gyms have been contacted for comment.
The gym opened in 2014 on the site of a former Chinese restaurant called Ruby.