The event will run until Saturday and includes more than 120 real ales plus a large variety of ciders, perries, fruit wines and mead.
There will be two beneficiaries of the event – St John Ambulance and the Billy Redmayne Memorial Fund.
The festival will be opened by the Lieutenant Governor Sir John Lorimer when he pours the first pint of festival ale that has been specially brewed for the occasion by Bushy’s Brewery.
The beer is called ‘Pegasus’ and a donation from each pint sold will be given to the Billy Redmayne Memorial Fund.
Billy Redmayne was a paratrooper under Sir John’s command during three tours in Afghanistan, and Manx Grand Prix winner, he died in a motorcycle race in Scarborough at the age of 25.
The charity, set up in his memory, aims to help newcomers at the Manx Grand Prix, as well as to help riders and their families after an accident.
Advocates Humphrey & Helfrich are the main sponsor of the popular annual festival.