This new round cements Uber’s place as one of the most richly valued private companies ever, along with other start-ups like Xiaomi, the Chinese electronics company valued by investors at around $45 billion, and Airbnb, the short-term lodging service valued at more than $24 billion.

It is also the latest fund-raising spree undertaken by Uber, which has added billions of dollars to its surging war chest. Uber has earmarked significant money for expansion into new markets like China, India and greater Southeast Asia. On Thursday, an Uber representative said the company had set aside $1 billion to spur growth specifically in India, where the company has faced stiff competition from local ride-hailing services.

Microsoft’s participation is a new development and may indicate a growing partnership between Uber and the software giant, which is based in Redmond, Wash. In May, a person familiar with the matter said this particular round of fund-raising was intended to form strategic alliances while simultaneously bolstering Uber’s coffers.

Uber has a history of bringing in important partners during funding rounds. In December, Baidu, the Chinese search giant, invested hundreds of millions in Uber. And in March, Times Internet, the digital venture of the Times of India Group media conglomerate, said it had agreed to a strategic investment in Uber.

Microsoft, too, has long invested in companies with which it may want to do business. In 2007, Microsoft paid $240 million for a 1.6 percent stake in Facebook, an investment that led to product integrations between the two companies. In the past, Skype video chat and Microsoft’s Bing search engine have been used to power Facebook software.