LA Fitness, which owns a chain of 66 gyms in the UK, is offering free membership until the end of August.
Teachers will be able to use equipment as well as take advantage of expert instruction to help them to kick-start their personal fitness regime. Fred Turok, chief executive of LA Fitness, said: "Exercise is proven to reduce stress levels and increase mental stimulation - both of which will be hugely beneficial to the teaching profession.
"We are hoping that during the school holidays, when time is not at such a premium, teachers will adopt an exercise programme that can then be adapted for when they go back to work."
Ron Clooney, 48, an English teacher at Chamberlayne Park school in Southampton, said: "It is a great idea. I was once a member of a gym but that lapsed a long time ago, so this is the perfect opportunity for me to get back into it."
The offer is valid for all teachers who register by July 19.
For more information, see www.lafitness.co.uk and enter the password "summer teachers". Contact details for your nearest gym are available on the website, or you can telephone 0870 990 7798