The 42.2 kilometre test of endurance will be held over Easter and will see participants run 212 laps of the centre's sporting field on their own or as part of a relay team.

The money raised will go to the McGrath Foundation's breast care nurses, who provide support to breast cancer patients and their families from diagnosis through to treatment.

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Inmates came up with the idea for the fundraiser - which has already raised over $10,000 - writing a letter to staff suggesting it was a chance to unite for a worthy cause.

"While treatments have improved, critical funding is still needed to support the brilliant women and men who are treating this disease and searching for a cure," the letter said.

"We hope the money raised can assist with research and help in the care for patients, throughout their treatment and beyond."

With almost 20,000 people diagnosed with breast cancer each year Governor Brad Peebles said they chose the foundation as both staff and inmates had been affected by this disease in some way.

"Inmates are largely powerless to do much for loved ones but are genuinely excited by the opportunity to help others via the McGrath Foundation," he said.

"Staff have helped inmates develop a strong social conscience. They want to show the community and their loved ones they are capable of pro-social and selfless action."

Marathon training has been under way at the centre for three months, with inmates undergoing rigorous practice runs, exercise regimes and aerobic exercise.

Family and friends of staff and inmates can sponsor participants on a per-lap basis, with a cheque to be presented to the McGrath Foundation next month.

Staff at the centre are also overseeing an inmate-led camera crew which is filming the marathon as part of a short documentary film.

Visit the McGrath Foundation to donate.