The move is seen as part of Didi's ambitions to become an international enterprise; over the past two years, Didi has acquired a stake in every major ride-sharing app.
In 2015, the Beijing-based firm invested $100 million in Lyft and merged the two apps together to better service Chinese consumers stateside. It also participated in a $350 million funding round for Southeast Asia's largest player GrabTaxi and sank an estimated $30 million in India's Ola. By Dec 2015, Lyft, Didi, GrabTaxi and Ola had formed a global rideshare partnership that reached nearly 50 percent of the world's population.
Last year, Didi then acquired rival Uber's business in China with the combined new company worth $35 billion.
An alliance with 99, which boasts over 10 million user downloads, marks Didi's first entry into Latin America. Sharing economy players are increasingly paying attention to Brazil, the world's second fastest-growing internet market, with French start-up BlaBlaCar starting operations there in November.
"China and Brazil are the world's foremost emerging markets with enormous opportunities for our ride-share industry," Didi CEO and founder Cheng Wei said in a statement.
"We look forward to working with more global partners in creating better mobility services for our cities as we reshape the future global transportation system."
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