Horrified Amelia Baines was left feeling "physically sick" after almost swallowing what she claims is the rotting creepy crawly as she took a bite of her McChicken burger.
The disgruntled diner took to the McDonald's Facebook page to complain after eating half of the burger and tasting "something strange".
According to her post, she had bought the sandwich meal on Tuesday from a McDonald's restaurant at the designer village in Mansfield.
The gruesome snack surfaced online soon after.
On McDonald's Facebook page, she wrote: "Yesterday I brought a McChicken sandwich meal from The designer village in Mansfield and after eating half my burger I took a bite and tasted something strange.
"I pulled it out to find a caterpillar! I felt physically sick.
"I've always thought McDonalds is clean, never had any problems eating there before and I was shocked to see what I had bitten into. Absolutely disgusted!"
In response, a spokesperson for the fast food chain said they were "really sorry to see this" and referred her to their customer services team.
In the comments section, Amelia described the discovery as "vile".
Others were equally repulsed, with one describing the skin-crawling finding as "disgusting".
Meanwhile, one joked: "At least the salad was fresh."
Daily Star Online have contacted McDonald's for comment.
Earlier this year a child was rushed to hospital after finding something disgusting at the bottom of a McDonald's cup.
And a mum as left retching when she realised she had bitten into a raw McDonald's burger.