Ben Dunne will close his doors to gym customers until a vaccine or effective treatment for Covid-19 is found.
The businessman said he could conceivably see himself having to lay off his 80 staff rather than the possibility of seeing people using his facilities dying from Covid-19.
Under Phase 3 of the Government's Roadmap to Reopening Business and Society, gyms have been allowed to open since June 29.
Speaking on RTE's Today with Sarah McInerney, Mr Dunne (71) said gyms are not a safe place during the pandemic.
"I'm not reopening my gyms because it's not safe to do so and until it's safe I don't believe in putting a product or facility in front of the consumer," he said.
"I have to put rules and regulations in my business and I have to make sure that they are kept.
"It's a laugh the way the regulations are being followed.
"If you go into a shop, people are not keeping distance and masks are mandatory but they're not being worn.
"I'm only looking after my business, and until I can keep my place safe, that the virus is under control and treatable or with a vaccine, I'm not opening.
"I don't believe gyms are a safe place for people at the moment."
Mr Dunne, who employs 80 people in his 10 Ben Dunne Gyms, said he can conceivably see himself going bust and having to lay off his staff as a result of the virus.
"I'm fully convinced that this virus is not under control," he said.
"We don't even know when or how it started and we're putting in place very stringent rules and regulations to try to keep in under control in the country.
"It's impossible to keep people apart, to make people wash their hands often enough, to stop people talking to each other, to keep their distance.
"I think we're heading for a deep, deep depression.
"My staff will be out of a job and I'll go bust, but I'd rather go bust than be burying people who are using my facilities when I knew they weren't safe. It's a possibility.
"It's facing me as plain as the nose on my face and it's facing other people as well, but they don't want to say it as openly as I do.
"This thing is going to devastate our country and many other countries unless we get in the right people. It can be fixed.
"I wouldn't dare to open. We're all in it together, and if we keep going the way we are we'll all go down together."