Visionary, ideologue, risk-taker: None of these shorthand labels quite capture who Elon Musk is. The billionaire entrepreneur is running two companies he cofounded that together employ 35,000 people. His aims are stratospheric. Tesla (TSLA), the automaker and sustainable-energy company that acquired SolarCity in 2016, is Musk’s pathway to a carbon-­emissions-free world. (The batteries he’s beginning to crank out at Tesla’s “Gigafactory” in Nevada are another element of that strategy.) SpaceX, an aerospace startup, was founded to lower the cost of space transportation and ultimately enable the colonization of Mars.

Musk, who has admitted to keeping a sleeping bag near a production line at Tesla’s factory in Fremont, Calif., has added another problem to his to-do list—soul-crushing traffic. His new business, the Boring Co., aims to find a way to quickly and cost-effectively dig networks of tunnels for vehicles and high-speed trains such as the Hyperloop, an idea he floated in 2013 that universities and startups are actively trying to develop.

Musk’s aura as a technocratic seer has taken some lumps over the past couple of years. Tesla—experiencing production delays and falling short of delivery goals—hasn’t always lived up to the bullish expectations of analysts and its legion of passionate fans. And the Tesla/SolarCity merger drew fire from critics who question whether the acquisition will benefit shareholders. But many still look to him as one of the tech world’s foremost civic-minded voices. Musk advises President Trump as part of the Strategic and Policy Forum.

This article is part of the 2017 World’s 50 Greatest Leaders list, our annual directory of world-changing leaders in business, government, philanthropy and beyond. Click here to see the entire package.