It will take place from 8 a.m. to 8 p.m. on Sunday August 24th - it's a Bank Holiday weekend - and will involve everyone from minis and juniors to 1st XV and vets.
The aim is for every player to be sponsored and there'll be other fundraising events during the marathon as well as family entertainment with Lee Maddison finishing the night off.
The day is being organised by a group of former players - including former Director of Rugby Kevan Oliphant - who've formed a committee to raise funds to provide an additional club bar in the new development.
The original plan to build a dedicated club bar had to be left out of the original scheme as costs escalated over the one million pound mark. There will be a double bar serving both rooms in the new 200 seater function room, but it's hoped that the money can be raised to buy the materials for the separate bar - and for members and supporters to use their skills and labour to build it.