Reddit co-founder Alexis Ohanian has resigned from the tech firm's board and urged the company to replace him with a black candidate.
The tech entrepreneur has also pledged to use future gains on his Reddit stock to "serve the black community."
In a series of tweets, he said he was doing it "as a father who needs to be able to answer his black daughter when she asks: 'What did you do?'"
It follows days of US protests against police brutality and racial inequality.
Mr Ohanian, who is married to black tennis champion Serena Williams, said he would be donating $1m (£800,000) to Know Your Rights Camp, a non-profit started by former NFL quarterback Colin Kaepernick.
"I believe resignation can actually be an act of leadership from people in power right now," he said in a video. "To everyone fighting to fix our broken nation: do not stop."
I really don't think its going to be pleasent what's coming
White men might be submissive for a while, inward and let things bottle up
But eventually we snap and when that happens its not going to be pretty
I really don't think its going to be pleasent what's coming White men might be submissive for a while, inward and let things bottle up But eventually we snap and when that happens its not going to be pretty