LONDON — Lakshmi N. Mittal, the chairman and chief executive of ArcelorMittal, the world’s biggest steel maker, is the rare business leader who applauds President Trump’s protectionist approach to trade.

For Mr. Mittal, the White House’s tariffs on steel imported into the United States have driven up prices, which, along with strong global demand, have delivered his company’s best results since 2011. On Wednesday, ArcelorMittal said profit rose to $1.9 billion in the second quarter, a 41 percent increase from the same period a year earlier, on sales of $20 billion.

The remarks, and the earnings, stand in stark contrast to fears voiced by companies and analysts in the United States and elsewhere over Mr. Trump’s protectionist push. The White House has imposed steel and aluminum tariffs on a wide range of countries, and, while it has pulled back in recent weeks on the threat of even more aggressive levies on some allies, several businesses have cited the uncertainty over trade as hurting business.

“The industry has quite changed,” Mr. Mittal said in an interview after ArcelorMittal reported its results. “Trade actions in various countries have really helped in structurally changing the landscape of the steel industry.”