The challenge grant donated by the 80-year-old billionaire financier is the largest he has ever made to an NGO, Soros's Open Society Foundations announced.
The grant challenged Human Rights Watch to match the gift with other private contributions.
Human Rights Watch said it hopes the grant and additional funds will enable it to set in place a plan for globalization, which will require it to increase its annual budget in five years from $48 million to $80 million.
The grant from Soros will be used to allow the organization to expand and deepen its global presence, the release said.
"Human Rights Watch is one of the most effective organizations I support. Human rights underpin our greatest aspirations: they're at the heart of open societies," Soros said.
"Human Rights Watch can have even greater impact by being genuinely international in scope .... In five years' time it aims to have as much as half its income and a majority of its board members come from outside the United States," Soros said.
"In an increasingly multi-polar world, we must ensure that Human Rights Watch's message resonates in the most influential capitals around the globe. Ending serious abuses requires generating pressure from any government with clout, including emerging powers in the global South," said Kenneth Roth, Human Rights Watch's executive director.