A US girl who discovered a discarded US$100 (A$135) scratchie discarded on the floor of a petrol station has sacrificed the winnings to help others.

Seven-year-old Missouri girl Phoebe Brown was visiting a highway Hy-Vee store on November 9 with her mother when she discovered the winning lottery ticket, local broadcaster FOX 4 Now reports .

"I saw that lottery ticket and it had a two on the back. I thought I'd better pick it up, and I told my mom it was a winner,” Phoebe recounted.

Mother Audrey Brown said she was left stumped by the discovery.

“Everything went through my mind. What could we do with it? What could Phoebe do with it?” she said.

Rather than spend the money on herself, the Year Two student decided to buy groceries, which she then donated to a school program dedicated to helping the less fortunate.