Ariana Grande Reveals Foot Injury Before 'Eternal Sunshine' Tour Finale

Ariana Grande is ditching her signature heels for the final stretch of her tour ... after suffering a painful foot injury.

Ari told fans Monday she'll be in "cozy footwear" for her London show -- and possibly Tuesday's finale -- because she's recovering from a deep cut underneath her foot.

She says it's not a sprain or muscular injury, but putting weight on the foot has been tough ... so the heels are staying backstage.

She joked fans may notice she's "a few inches shorter than usual" onstage ... but made it clear the injury won't keep her from performing, writing, "but please do not fret. on with the show and i am on the mend!"

The timing is certainly less than ideal ... Ariana is wrapping up her 10-show run at London's O2 Arena, with the "Eternal Sunshine Tour" scheduled to end Tuesday after nearly three months on the road.

As TMZ previously reported ... Ari has also said she plans to step back from the public eye once the tour is over.