Ritchie, who died Sunday, was nicknamed the "Angel of the Gap."
He lived across from an ocean cliff known as The Gap on South Head in eastern Sydney for more than five decades. The Gap is a place where many people have gone to commit suicide.
In the early years, Ritchie said he would physically restrain people from jumping off the cliff while his wife called police, but in later years he tried a simpler approach.
"[I'd say] 'What are you doing there? Why don't you come to our place across the road and have a cup of tea?'" Ritchie said.
Authorities estimate Ritchie saved more than 150 lives while he lived across from The Gap. He said he believed other people would have done the same thing, the Australian Broadcasting Corp. reported.
"You can't just sit there and watch them, I mean you've got to do something about it, anybody's like that. It gives them the chance of changing their lives," he said.
Ritchie, who worked as a life-insurance salesman most of his life, received an Order of Australia for his suicide prevention efforts at The Gap and was named last year's Australian Local Hero of the Year.
Member of Parliament Malcolm Turnbull said Ritchie was one of the greatest Australians.
"Don Ritchie, whose courage and compassion saved so many lives at the Gap, died yesterday. A true hero, one of our greatest Australians. RIP," he said on Twitter Monday.