Katy Perry is in a toe jam, after a woman claims she lost one of hers while working on the singer's tour.

Christina Fish claims in a lawsuit she was hired as a stagehand for Katy's Prismatic World Tour in 2014.

On the night of Katy's Raleigh, NC concert she was asked to help move a wall ... when it got stuck and then rolled across her foot. She says she felt her shoe fill with blood.

She says she was offered ice but no one called for an ambulance, so she had to call a friend to pick her up and take her to the ER.

Christina says her right toe became gangrenous, and eventually needed to be amputated. She says she wasn't able to use her foot for months.

She also says she suffered great emotional distress, because orthopedic doctors instructed her to keep her "dead toe" on as long as possible before the eventual amputation.

Christina says she had a passion for yoga and that's now a distant memory without a toe.  

She's suing Katy, Live Nation and a bunch of stage production companies for a whole lot of money.