The OSF announced the move on Tuesday, blaming "an increasingly repressive political and legal environment." The foundation, which is funded by Soros and supports civil society groups around the world, said it will continue to support its work in Hungary and channel funding to projects from it's office in Berlin.
"The government of Hungary has denigrated and misrepresented our work and repressed civil society for the sake of political gain, using tactics unprecedented in the history of the European Union," OSF president Patrick Gaspard said in a statement.
Speaking after his election victory, Orban said: "I know they [the OSF] won’t accept the result of the election, they will organize all sorts of things, they have unlimited financial resources."
The attacks on OSF, which the NGO says are unfounded, were a core element of Orban and his Fidez parties' political campaign which saw them re-elected for a third term with almost 48% of votes.
Orban has increased his power over the media and put allies in control of institutions that were previously independent. He fell out with both Soros and the EU over the 2015 financial crisis and his stance on restricting immigration.
The Fidez party initiated the "Stop Soros Act" in February. It enables the interior minister to ban NGO's working on immigration citing possible "national security risks." It requires foreign-funded NGO's, like OSF to pay 25 % tax.
Soros, born in Hungary and a Jewish survivor of World War II, is worth around $25 billion and is best known in the UK as "The Man who broke the Bank of England" after he bet big against the pound in 1992 and made more than $1 billion.
The Hungarian billionaire has faced attacks in recent months from populists and nationalists who denounce his support for liberal causes.
Soros attacked his critics in a January interview with the Financial Times, saying that the dominant ideology in the world now is nationalism. He added that he believed Putin was behind many of the attacks on him.
"It's déjà vu all over again with one big change — the dominant ideology in the world now is nationalism," said Soros. "It's the EU that's the institution that's on the verge of a breakdown. And Russia is now the resurgent power, based on nationalism."