Free donuts! (Upon purchase.)

Krispy Kreme lovers can stop by anytime between now and October 14 for a free frosting, but there’s a little catch.

To get your hands on the sweet treat, you’ll need to show a McDonald’s receipt dated between October 10 and 14.

The fried promotion is being rolled out to celebrate the bakery’s new partnership with the Golden Arches, which will see Krispy Kreme donuts sold at all 13,500-plus McD’s locations by the end of 2026.

Chicago, home of the Hamburglar, has reportedly been tipped as the first market to get the expanded offering.

“The number one request we receive from consumers is for more access to our delicious, fresh donuts. Having Krispy Kreme donuts under the Golden Arches is worth its weight in gold to our fans and we are excited to celebrate by giving our guests who also visit a McDonald’s a free Original Glazed donut,” said Josh Charlesworth, president and CEO of Krispy Kreme in an announcement.

Ultimately, all U.S. McDonald’s customers will be offered the original chocolate glazed ice cream with sprinkles and chocolate ice cream filled donuts, individually or in packs of six, a Krispy Kreme spokesperson previously confirmed to The Post.

The length of the ramp-up period is reportedly due to the amount of production capacity Krispy Kreme will need to meet the demand from so many McDonald’s stores.

The North Carolina-based chain only has between 300 and 400 company-owned stores. It has thousands of other so-called ‘access points’, such as supermarkets and convenience stores.

Times Square in New York is home to the chain’s largest store.

The fried snack maker was the victim of a somewhat hilarious robbery last year, when a sticky-fingered bandit in Australia stole a van with about 10,000 donuts in the back.

The vehicle was found abandoned days later.