Gavin Tiffin, head of hospitality at Guy's and St Thomas', will this summer cycle 2,000 miles from London to Russia to raise money for charities linked to the hospitals.
Gavin, 34, will be the first person ever to attempt the gruelling route through 10 different countries in just three weeks.
Starting at St Thomas' Hospital and finishing in St Petersburg, he will also host events while on his journey, The Cultural Cycle, to raise awareness about how the arts can be used to aid hospital recovery.
Gavin originates from Crieff in Scotland and has worked at the hospitals for more than four years. He said: "My mission is to promote and raise awareness of how we can use music and the arts to make people's lives better.
"They have amazing healing powers and play a huge role in the recovery of patients at Guy's and St Thomas' and Evelina London Children's Hospital.
"The money I raise from my challenge will go to Breathe Arts Health Research, MediCinema and Evelina London Children's Hospital.
"I'm lucky enough to work with these amazing charities and will witness firsthand the difference my fundraising will make."
MediCinema was founded at St Thomas' and now runs six state-of-the-art cinemas in hospitals across the UK.
Originally part of Guy's and St Thomas' Charity, Breathe Arts Health Research now provides creative projects in different London hospitals to improve the recovery and experience of patients.
Evelina London Children's Hospital sees over 55,000 children a year from south London and the south east of England and needs help to fund everything from life-saving equipment and research, through to the little touches that make a visit to hospital more comfortable.
Gavin added: "I hope to raise tens of thousands of pounds for my chosen charities by cycling more than 100 miles a day and holding special events as I reach Berlin, Poznan and Warsaw.
"I'd love for people to get involved by joining me on the first leg of my journey from London to Dover, or by hosting their own fundraising events.
"I'll be cycling solo with a support vehicle following, and hopefully I'll pick up some supporters en route. I'll be sharing my journey with everyone on social media."
Gavin will begin his challenge at St Thomas' Hospital on 13 August and end in the heart of St Petersburg on 3 September.
"I chose St Petersburg as my finishing point for two reasons. Firstly, my wife Anna is Russian, and also this year marks the 70th anniversary of VE day.
"As the grandson of a Royal Navy veteran who delivered much needed supplies to Russia during the war, I am honoured to be finishing my challenge where he served."