A hedge fund billionaire who was an economic adviser to President-elect Donald J. Trump during the campaign has taken a position in a fast-growing Chinese ride-sharing company that recently signed a deal to acquire Uber Technologies’ operations in China.

John Paulson, who made $15 billion betting against the housing market before the financial crisis, told his investors on Wednesday that at least one of his portfolios had taken an investment stake in Didi Chuxing, a privately owned Chinese company, said people briefed on the matter who were not authorized to speak publicly.

The investment, by Mr. Paulson’s Advantage funds, is roughly 7 percent of the assets of those portfolios, he told investors, these people said.

Didi Chuxing, which has backing from Alibaba Group and Apple, could prepare for an initial public offering in the next year, according to news reports. In August, Didi struck a deal with its main rival, the American ride-hailing giant Uber, to acquire Uber China in a transaction that created a company some valued at $35 billion.