A notice on the door of Snap Fitness says the gym was to close on December 31, and would not re-open.
Eyewitnesses said the firm was already removing equipment from the gym today, Thursday January 2.
The gym opened in empty units beneath the Travelodge in September 2017, offering round-the-clock access to exercise machines.
At the time, Arndale manager Sarah Harrison said the move would “totally transform the area” and “sends a positive message about the town centre”.
Snap Fitness also has a gym underneath the Travelodge on the corner of Spring Garden Street in Lancaster, which opened in April 2016.
There are more than 2,000 Snap Fitness clubs worldwide and 35 in the UK.
The gym offers the latest training equipment as well as group classes.
A spokesman for Snap Fitness said: “I can confirm that regrettably Snap Fitness Morecambe did close its doors on 31st December 2019.
“The current economic climate meant that it was no longer feasible for the franchisee to continue to operate that facility, however our other locations within the UK continue to enjoy great success.
“We have very much enjoyed operating the Morecambe facility since its opening in 2017 and thank the Morecambe community for a wonderful few years.”