Donald Trump will name Wilbur Ross Jr. as commerce secretary, a transition official said Tuesday, selecting a fellow businessman whose name rings out in the Rust Belt.

In 2001, with the steel industry in crisis and more than 30 steelmakers in bankruptcy, Mr. Ross swooped in and bought key assets, such as LTV Corp., Bethlehem Steel and Weirton Steel Corp.

By cutting jobs and legacy costs, as well as negotiating new deals with unions, he was able to put mills back on their feet, before selling them at a profit.

For some, this made the 79-year-old New Jersey native nothing short of a savior of the steel industry—someone willing to risk his money to save thousands of jobs. For others, he was a vulture who cut jobs and pensions, and forced pain on a once proud industry.

It’s a role that Mr. Ross, in a storied and wide-ranging Wall Street career, has played in other industries, including auto parts, coal and textiles.

He even represented bondholders in Mr. Trump’s Taj Mahal casino in Atlantic City. The creditors were angry about a possible missed payment and debated whether to seize control of the casino. Mr. Ross argued that Mr. Trump’s properties were worth more with the man involved and helped negotiate a plan to keep him in charge.

Mr. Ross eventually became a key Trump ally, backing his campaign for president and helping him raise money from Wall Street executives.

Wilbur Ross Jr. Age : 79.

: 79. Résumé : Chairman and chief strategist of W.L. Ross & Co., a private-equity firm. He has extensive experience in corporate restructurings. In the early 1990s, Mr. Ross represented bondholders in Mr. Trump’s struggling casino businesses, which he said gave him ‘great respect’ for the president-elect.

: Chairman and chief strategist of W.L. Ross & Co., a private-equity firm. He has extensive experience in corporate restructurings. In the early 1990s, Mr. Ross represented bondholders in Mr. Trump’s struggling casino businesses, which he said gave him ‘great respect’ for the president-elect. Notable stance: Mr. Ross has become a top critic of trade deals like Nafta.

But it’s in the steel industry’s consolidation that Mr. Ross arguably made his largest mark. “He was the right person at the right time,” when steelmakers were struggling, said John Surma, former CEO of U.S. Steel Corp., in an interview.

Even some former adversaries acknowledge that in addition to cutting thousands of jobs, Mr. Ross played a major role in a restructuring that preserved other jobs.

“There’s no denying he saved thousands of jobs,” says Charles Bradford, now an independent analyst, who worked for banks and investors that mounted competing restructuring proposals to those of Mr. Ross in steel bankruptcy proceedings. “He doesn’t like to be called a vulture, but a vulture investor is somebody who finds a distressed asset that still has good bones and turns it around and flips it. And that is what he did.”

In 2002, for example, Mr. Ross’s company W.L. Ross & Co. bought the assets of LTV Corp., once the nation’s third-biggest steel mill, for $125 million in cash and $200 million in environmental and other liabilities. At the time, Mr. Ross said the new company would employ about 3,000, less than half of the 7,500 LTV had employed.

In 2005, Mr. Ross sold his International Steel Group Inc., to the world’s largest steelmaker ArcelorMittal for $4.5 billion, netting billions in profits. Mr. Ross is still an independent director on ArcelorMittal’s board, one of many business ties he would have to sever if he joins the cabinet.

“He was the force assisting in the consolidation of the steel sector,” says John Packard, publisher of Steel Market Update. “He managed to save mills that might have been shut down if they hadn’t been consolidated.”

Mr. Bradford recalls that when he went up against Mr. Ross, the latter usually won. “When we asked clients why he won, they said, ‘He was nastier, he worked harder for whatever side he was on,’ ” Mr. Bradford said.

Mr. Ross, the son of a lawyer, grew up in suburban New Jersey and dreamed of being a writer. Instead, he went to Wall Street and became a bankruptcy specialist at Rothschild Inc. in the 1970s, working on high-profile bankruptcies and restructurings, including Texaco, Continental Airlines and TWA.

His career as a Rust Belt investor hasn’t been without blemish. In 2006, an explosion at a mine in Sago, W.Va., under control of his International Coal Group Inc., killed 12 workers, prompting criticism of ICG’s safety precautions.

Mr. Ross called it “the worst day of my life.” In a statement, he added, “I don’t know what is harder—trying to get to sleep at night with Sago hanging over me or getting up in the morning to face another day of internal sorrow and external criticism.”

Corrections & Amplifications:

Wilbur Ross is 79 years old. A chart accomanying an earlier version of this article incorrectly stated that he was 78. (Dec. 1, 2016)

Write to John W. Miller at john.miller@wsj.com