Grab was introduced in 2012 and now operates in eight Southeast Asian countries: Cambodia, Indonesia, Malaysia, Myanmar, the Philippines, Singapore, Thailand and Vietnam. And it has put up a tough fight.

With passengers in nearly 200 cities across the region, the company is aiming to be more than just a transportation provider. It wants its digital wallet, GrabPay, to replace cash as a way to pay for things at offline shops and restaurants. And in a region where many people lack credit histories or even bank accounts, Grab is undertaking a venture to make loans to consumers and small businesses. Data collected through Grab’s app, on users’ movements and transactions, is used to assess their creditworthiness.

Grab also offers a wide variety of ways for people to get around. In Singapore, you can hop on a GrabShuttle that, like a public bus, will take you between points along a fixed route. In jam-packed Jakarta, you can use Grab’s app to hail a nearby motorbike taxi right off the street, forgoing the usual process of prebooking and waiting for the driver to arrive at your location.

The company is generally regarded as the market leader in Southeast Asia. But in Indonesia, the region’s most populous country, it is taking on Go-Jek, a local rival whose apps offer services, such as massages on demand and motorbike parcel deliveries, that go beyond just rides. Go-Jek’s investors include Google and Tencent, the Chinese internet conglomerate.

In an interview, Ming Maa, Grab’s president, said that the deal with Uber would help Grab move closer to profitability, although he declined to give specifics. One key benefit of combining with Uber, Mr. Maa said, is that it immediately expands Grab’s food-delivery operations.

“That has massive, massive benefits to our consumer base,” he said, “but is also a key driver for our mobile payments business.”

For Uber, ceding Southeast Asia still leaves it with plenty of challengers elsewhere in the world. Didi Chuxing, based in Beijing, invested alongside SoftBank in Grab last year. It recently raised money from SoftBank and other investors at a valuation of $56 billion — higher than the $48 billion at which Uber was valued as part of last year’s stake sale to SoftBank.