The billionaire, who has praised plant-based meat in the past for its environmental impact, said he will use his free time to focus on the Bill & Melinda Gates Foundation.
According to Sky News, Gates said: "I have made the decision to step down from both of the public boards on which I serve - Microsoft and Berkshire Hathaway - to dedicate more time to philanthropic priorities including global health and development, education, and my increasing engagement in tackling climate change.
"I am looking forward to this next phase as an opportunity to maintain the friendships and partnerships that have meant the most to me, continue to contribute to two companies of which I am incredibly proud, and effectively prioritize my commitment to addressing some of the world's toughest challenges."
Gates added that Microsoft would 'always be an important part of my life's work' and that he will continue to be involved in its leadership.
'Don't eat meat'
In a recent video with major YouTuber Mark Rober, Gates discussed the environmental impact of meat.
“The agriculture sector is about 18 percent of overall emissions, but livestock is about half of that 18 percent. Almost all of that is beef," he said.
"One of the great tragedies about climate is that it's the poorest in the world, the farmers who live barely near to the equator, that all this heat and flooding and droughts - they're going to suffer by far the most.
"If you're just trying to get people to cut back, don't eat meat, don't drive to work, don't take trips - it's such a dramatic set of sacrifices that everybody has to engage in that without innovation we're probably going to go way past the two degrees."