The multi-millionaire founder of Kwik Save is to fulfil a "pact with God" he made as a struggling young man and donate half his fortune to the Church.
Manx-based Albert Gubay, 82, a life-long Roman Catholic who was born in Wales, has placed his business empire, valued at £600m, into a trust.
The money will be passed into a charitable foundation on his death.
He founded the Kwik Save supermarket chain and has property developments in Liverpool and Manchester.
Mr Gubay, originally from Rhyl, Denbighshire, is ranked 107th on The Sunday Times Rich List in 2009, with a £480m estate.
Half of his money will go to causes identified by the Roman Catholic Church, with the other half to go to good causes selected at the discretion of the trustees.
He spoke in a 1997 TV documentary about emerging from the Royal Navy after World War II in his demob suit and with £80.
He said he had borrowed £100 and had made a pact with God at the time - "make me a millionaire and you can have half of my money".
Mr Gubay said: "I want to carry on supporting good causes, but my whole focus in the next few years is to work as hard as I can to meet my target of a £1bn charity."
Mr Gubay founded the first Kwik Save supermarket in 1965 and sold it for £14m in 1973. The company went into administration in 2007.
The Albert Gubay Charitable Foundation is chaired by trustee John Nugent who said the millionaire had always been a frugal man who wanted to ensure his money had a purpose.