A McDonald's customer has sued the company, claiming it used artificial intelligence to keep menu prices high. The proposed nationwide class action was filed Friday in federal court in Chicago, Reuters reported. It accuses McDonald's of breaking the Sherman Act, the main federal antitrust law.

The plaintiff is Michael Thomas, Law Commentary reported. The suit says McDonald's used an AI pricing engine across nearly 14,000 U.S. restaurants, most of them run by franchise owners. It claims the tool let those separate owners move prices together.

The suit makes several claims that have not been proven. It says McDonald's has used the pricing system since at least 2019. It also says the company made taking part mandatory for franchisees in January 2026.

The complaint points to wide price gaps. A Big Mac cost $5.69 at one Fresno, Calif., restaurant and $6.89 at another about two miles away, according to Law Commentary's account of the filing.

McDonald's pushed back hard. "AI does not set the price of a Big Mac," the company said, according to Reuters. It said franchise owners decide their own prices.

The plaintiff's lawyer, Lark Turner, said the system was built to "nickel-and-dime consumers down to the last French fry."

Here's why it matters for diners. Fast food prices have climbed sharply in recent years. The suit seeks money for people who say they paid too much.

There is some history here too. Lawsuits over shared pricing software have hit other industries, including apartment rentals and hotels. Those cases argue that when one tool sets prices for many sellers, it can act like an illegal price-fixing deal even without a handshake.

What happens next: A judge must first decide whether the case can go forward as a class action covering customers nationwide. That step can take months.

What we know: The suit was filed Friday in Chicago and seeks nationwide class status.
What we don't: Whether a judge will let it proceed, and what the pricing data actually show.