"The trust is the latest piece in our mosaic of 2010 FIFA World Cup-related legacy activities for South Africa and the African continent," Blatter said. "This is also a reward for South Africans for having been such great hosts."
Another $20 million had been given to South Africa in the build-up to the June-July tournament, FIFA said in a statement.
"We have always said that the first FIFA World Cup on African soil should leave a lasting sports and social legacy once the tournament is over," Blatter said. "This trust is yet another concrete achievement in this area."
FIFA said auditors Ernst and Young would administer the trust, to ensure that all the money was spent on projects that would benefit the public. South African President Jacob Zuma, who appeared with Blatter at a news conference in Soweto, said the Cup had helped to cushion his country's economy from the global downturn and contributed to economic growth for this year.
"Now remains the difficult but most important task of ensuring a lasting legacy and to build world-class national teams both at youth and senior level," Zuma said in a statement.
"The FIFA World Cup Legacy Trust which is being launched today is an important contribution to the achievement of that goal."
At the news conference, Blatter said this month's decision to award the 2018 and 2022 World Cups to Russia and Qatar respectively was based on spreading the sport around the world and not on financial reasons.
"We shall go to new territories," Blatter said. "Don't speak about money. This has nothing to do with money."
Blatter has previously rejected allegations of corruption, after criticism from media in the United States and Britain, and called England's unsuccessful bid team "bad losers".
The 2018 Cup in Russia will be the first staged in Eastern Europe after 10 editions in the western half of the continent.
Qatar will be the first Middle Eastern and first Arab country to host a World Cup, and also the smallest nation.
Asked whether gays and lesbians should worry about attending the World Cup in Qatar because of its hostile attitude toward homosexuality, Blatter quipped: "They should refrain from any sexual activities."
He swiftly went on to say that FIFA would not tolerate any form of discrimination and that he was sure that everyone would be able to attend and enjoy the World Cup in Qatar.
