The 27-year-old Oosthuizen, a 200-1 long-shot to win the Major championship at the start of the week, is a graduate of the Ernie Els Golf Foundation which helps identify young talent in South Africa. "This is absolutely unbelievable," Els said.
"It would be difficult to find anybody in the world who is more proud of him right now.
"He comes from a little town on the outskirts of George in South Africa and needed help so we took him into the foundation and educated him and sent him to various tournaments around the country and also the world.
"I could not be happier. He is our first Major champion and has made us all very proud."
Els, who won the British Open on the Scottish links of Muirfield in 2002 and also triumphed at the US Open in 1994 and 1997, said there was no chance fame would go to Oosthuizen's head after becoming South Africa's sixth Major winner.
"Louis is now the Open champion," said the player known as the 'Big Easy'. "His life will change, he won't.
"He is simply a wonderful kid. You cannot find a better one." Els said he always knew Oosthuizen, was capable of joining golf's elite.
"I thought long before anybody had heard of him that he was going to be an exceptional player," said the 40-year-old. "He has shot an absolutely stunning 57 at Mossel Bay (on the Western Cape) which will neither be equalled nor bettered. "You have something special when you do that. The world might know about him now but even before today he had started his own foundation to help kids who are needy.
"They could not have a better role model. Louis cares and he is giving back. He's that sort of person. The kid is different class."