Danica Patrick returns to racing. On foot.

Danica Patrick is no stranger to racing, but on Monday she will be competing in a different kind of race as she runs her first marathon.

“I have only ever had one bucket list item. 1! That is to do a marathon,” she wrote on Instagram. “So, why not do the most famous and apparently hardest one … Boston.”

Patrick, who retired from racecar driving in 2018, is running in bib number 500, a nod by race organizers to her trailblazing accomplishments at the Indianapolis 500 and Daytona 500.

Patrick is the honorary team captain for Team Speed of Light, the fund-raising arm of a foundation started by the former New England Patriot Matt Light that helps young people develop skills for their future through the outdoors.

“It’s no secret that I love a tough challenge,” she wrote on a team fund-raising page for the race. “I’ve never ran a marathon, so why not do the most historic and iconic one first.”

Patrick shared her training — and what she’s learned from it — with her followers. She noted the benefit of being in tune with her hydration and nutrition, what she’s wearing to run, the temperature and available shade. But Patrick also realized the mental game that is distance running, sharing on Instagram, “when I need my mind to shift from pain to something good … with some effort, I can.”

Runners typically have to qualify for the Boston Marathon, completing at least one 26.2 mile race before. By running to support a charity, Patrick is able to run Monday’s race as her first. She is running with a group that includes her sister, Brooke Selman.

“Can’t wait to join my fellow runners for the race of a lifetime,” she wrote.