George Soros is to donate $100m (£65m) to Human Rights Watch (HRW) over the next 10 years, the investor and philanthropist has announced.
"Human Rights Watch is one of the most effective organisations I support," Mr Soros said.
The gift from Soros's Open Society Foundations is the largest the billionaire has made to a non-governmental organisation, HRW said.
It is given under the condition that HRW raises another $100m.
The gift is the first in a series of large donations he plans to make, Mr Soros said in an interview with the New York Times.
"This is partly due to age," the 80-year-old added.
"Originally I wanted to distribute all of the money during my lifetime, but I have abandoned that plan".
HRW is to use the money to hire more staff and expand its work internationally, the group said in a statement.
The plan requires HRW to increase its annual budget from $48m to $80m within five years, the organisation added.
HRW, which is based in New York, currently has a staff of almost 300 and a presence in nearly 90 countries.
In October, Forbes Magazine estimated Mr Soros's fortune at $14bn (£9.1bn).
BBC News
