Playing cowboys and Indians is truly a thing of the past — and that includes dressing up as either of those characters for Halloween.

Singer/actress Hilary Duff found that out over the weekend when she and her new boyfriend — personal trainer Jason Walsh — went to a Beverly Hills Halloween party.

“I am SO sorry to people I offended with my costume.”

Duff, 29, dressed as a “sexy pilgrim” — in fishnets and a pilgrim top. Walsh went for full-blown Native American chief. Social media jumped all over them for being “insensitive” and “ignorant” and “racist” — by reinforcing negative stereotypes.

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“HILARY DUFF YOUR COSTUME IS SO YESTERDAY,” one Twitter user wrote.

Another said, “No @HilaryDuff Traditional dress is not a costume and you being dressed as a pilgrim proves to me how insensitive and ignorant you are.”

“Look at how much work dude put into being racist,” tweeted another person about Walsh’s elaborate costume.

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The star’s apology comes on the heels of Chris Hemsworth’s apology for dressing as a Native American at a 2015 New Year’s Eve party.

It was a Lone Ranger-themed party and he wore the “traditional dress of First Nations people,” he wrote on Instagram, calling it a “thoughtless action.”

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Meanwhile, students at The University of Texas at Austin have been advised not to be Indians — but even more crazy is that they’ve been told not to wear cowboy boots or cowboy hats on Halloween. In Texas, no less.

Fraternities and sororities were instructed to avoid Halloween party costumes and themes that might “appropriate another culture or experience,” according to The College Fix.

It lists 11 separate “harmful” themes, including any “generalized representation” of Asian culture or “Indigenous” cultures, such as “Cowboys and Indians,” as well as “tropical” or “fiesta.”

The guide addresses white people, too, noting “harmful” themes as including “Golf Pros & Tennis Hoes,” “Trailer Trash,” and “Chicks and Hicks.”

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Also apologizing for his costume this year is college student Brock Denton, who decided to dress as Bill Cosby for a fraternity party at University of Central Arkansas, as The Washington Post reported.

Denton, who is white, covered his skin with black paint. He posted a photo on Instagram (long since taken down) and widespread outrage ensued.

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The fraternity has been suspended and Denton issued an apology. “I have been sent death threats, threats to burn my house down. I am scared for my life,” he wrote.