McDonald’s will stop using plastic foam cups, which keep drinks icy cold but make environmentalists red hot, by the end of this year.

The world’s largest restaurant operator quietly disclosed the decision on its website, along with its plan to use recycled and certified sources for all of its fiber-based packaging by 2020.

“We also plan to eliminate foam packaging from our global system by the end of 2018,” the company states on its website.

It’s the first time the fast-food giant has openly committed to a deadline to completely stop using polystyrene drink containers, which are eco-unfriendly and nearly impossible to recycle. The containers for its large cold drinks represent a mere 2 percent of its packaging, which still comes out to millions of dollars and cups annually.

The decision is expected to ease tensions between McDonald’s and shareholder activists, who last year pushed the Oak Brook-based company to assess the environmental damage caused by using foam containers.

McDonald’s for years has been using more environmentally friendly paper wrappings and containers but it’s taken a lot of flak for its plastic foam cups.

Last spring, the company beat back a nonbinding shareholder resolution aimed at ending foam container usage that garnered a surprisingly strong 32 percent of votes cast.

In July, the Tribune reported that McDonald’s was reintroducing the plastic foam cups in the Chicago area. Environmentalists told me the cups also were being used in other parts of the country and internationally — an assertion McDonald’s declined to address.

At that time, this column chided the company’s decision to go with foam cups as a tone-deaf throwback to McDonald’s old-school selling ways.

Some McDonald’s franchisees, operators and customers like the utility of the cups. But their use undercut CEO Steve Easterbrook’s modernization efforts, including his outreach to young adults — many of whom prefer to do business with socially responsible organizations.

McDonald’s, which is relocating to Chicago, did not respond to my request Wednesday to talk about its plans.

One satisfied constituent is California-based As You Sow, a corporate responsibility group that sponsored last year’s shareholder resolution at McDonald’s. It planned to introduce a similar resolution calling on the burger chain to assess the environmental impact of foam packaging this year but will drop those plans in light of the McDonald’s move.

McDonald’s is expected to announce a packaging and recycling initiative later this week, said Conrad MacKerron, a senior vice president of As You Sow. “We do appreciate what McDonald’s has done,” he said. “It’s taken a long time, but better late than never.”

It’s been nearly 27 years since McDonald’s made big news by getting rid of polystyrene “clamshells” for its hamburgers and other food items, replacing them with specially treated paper-based wrappings.

McDonald’s decision to completely stop using polystyrene will hopefully resonate with other fast-food providers, including Dunkin’ Donuts and Chick-fil-A, which remain purveyors of this dodgy packaging.

Internationally, McDonald’s decision is expected to help curtail the use of foam packaging in growing Asian markets, where fast-food companies are expanding and recycling efforts are becoming increasingly important.

“It sends a global signal and that’s of value,” MacKerron said.