Uber Technologies Inc.'s whopping valuation of $18.2 billion is a bet by some of the world's top investors that the car-hailing smartphone app can grow by expanding world-wide and branching into new arenas, like logistics.

The five-year-old company said on Friday that it has raised $1.2 billion from a consortium of investors led by mutual-fund giant Fidelity Investments.

The big infusion, following weeks of competitive bidding among investors, highlights some investors' belief that Uber is among a group of mobile apps disrupting traditional industries. In just four years, the service has become part of daily life for users in more than 130 cities and generated enough demand to turn a profit in several of its top markets.

"It's probably the fastest international expansion that I've ever seen from a venture-backed company," Bill Gurley, a venture capitalist at Benchmark, which invested in Uber in 2011. Mr. Gurley said Benchmark remains Uber's largest institutional shareholder.

Uber's smartphone app, which lets users hail cars driven by both professional and nonprofessional drivers, is part of the so-called sharing economy, where people use online tools to sell time or resources to others.