Chinese smartphone maker Xiaomi is now the world's most valuable startup.

On Monday, the company announced that it has closed a $1.1-billion round of new funding that puts its valuation at a whopping $45 billion. This makes it more valuable than the San Francisco ride-hailing startup Uber, whose latest round of funding earned it a valuation of $40 billion.

Revealed on Facebook by Xiaomi co-founder and president Bin Lin, the news underlines the rapid ascent of this four-year-old company. After swiftly taking hold of the Chinese smartphone market with low-cost phones based on the Android mobile operating system—a conquest led by former Google man Hugo Barra—Xiaomi is now the world's third largest smartphone manufacturer. According to a recent report from research outfit Gartner, Xiaomi sold 16 million units in the third quarter of 2014, up from 3.6 million in the same quarter last year.

This was the highest growth of any smartphone vendor during that period, Gartner says. Sales from the world's biggest manufacturer, Samsung, declined by 29 percent.

Earlier this month, a Xiaomi regulatory filing from the company showed it pulled in $56 million (437.5 million yuan) in 2013—a far cry from the $25.4 billion that Apple made in China last year. According to a spokesperson for the company, this filing did not cover the entirety of Xiaomi’s business, but it seems to indicate that the company is operating on rather thin margins. Whatever the case, it has ridden its low-cost strategy to enormous growth.

Now, the company is eying even bigger conquests, moving its low-cost phones into India and Brazil. But in places like India, it faces concerns over its Chinese roots, with some worried that the Chinese government will snoop on the internet services that Xiaomi phones provide to consumers.

Update 1:27 PM EST 12/30/2014: This story has been updated to show that, according to a Xiaomi spokesperson, the recent regulatory filing involving Xiaomi does not cover the company’s entire business.