She’s the marathon’s sole survivor.

Brynda Mara Grube, a 41-year-old Upper East Sider, ran the TCS New York City Marathon yesterday in five hours and 53 minutes, completing her third 26.2-mile race since 2016. And she did it barefoot.

“I have more respect for the street cleaners of New York City than ever before,” says Grube, who tells The Post she ran shoe-less to bring awareness to climate change and indigenous populations affected by it.

What Grube lacked in footwear she made up for in accessories, which she collected over the years from tribes around the world. Items included a bracelet from a Navajo tribe in Arizona, foot jewelry from a tribe near Cape Town, South Africa, necklaces from Amazon tribes, and a headdress from an indigenous group in Papua New Guinea.

Her grass skirt came from Havana, but she had trouble tracking down a top.

“I wanted it to be natural, so I thought about going topless, but I thought it might hurt my breasts,” says Grube, a Kingsborough High School ESL teacher originally from Brazil. Instead, “I took a leather belt and bound my breast with one, and put two more, on the top and bottom to keep it in place.”

Grube, a world traveler who says she has indigenous ancestors, plans to run the Berlin Marathon in the same get-up.

This wasn’t her first time pounding the pavement with bare feet. Grube’s first barefoot race was the Rockaway Beach Triathlon at the end of September — back when it was a little warmer, at least.

“When it came time to run the 3 miles, I just didn’t pick up my shoes. I thought, ‘I’m going to run this barefoot, for my tribe and all the tribes in the Amazon, and around the world that are suffering.’ ”

The mother of one said she ended up with some gnarly blisters.

“I remember one bubble got really black, so I went to Google, and I found other people who barefoot run and they said they have it too, from calluses and blisters. I decided I would be OK.”

But she ultimately ran 6 miles — and eventually 18 miles — sans shoes in the lead-up to the big race.

“Brooklyn was the craziest, it had the most potholes,” she says. “A lot of the [potholes] that were fixed were filled with gravel [and] that could be nasty. I ran my foot through the pavement four or five times to get gravel off.”

Luckily, she steered clear of more hazardous road conditions: “I only saw glass two times and I was able to avoid it.”

Her only other major foe on the course? “Acorns. When they break, they will go into your foot and it hurts like hell.”

Today, she says she woke up “tired but not exhausted,” and her thighs didn’t hurt quite as much as in previous years, when she wore sneakers. Her feet are another story.

“I went to a pedicurist, and she managed to get most of the dirt out,” she says.

As for her cause, the social justice runner may have to resort to other methods to help raise awareness for indigenous tribes.

“No one recognized the Papua New Guinea flag on my head,” she says in a video uploaded to her Instagram after the race. “They kept saying ‘Pocahontas!’ and ‘Moana!’ and ‘Great costume!’ and not really focusing on the message.”