The 82-year-old was about to cook chips for dinner when she spotted the reptile and slammed the door shut.
She thought her eyes were playing tricks on her after recently undergoing a cataract operation, the Manchester Evening News reports.
But an RSPCA inspector soon arrived and rescued the snake, while the woman and her husband ordered from a fish and chip shop instead.
It turned out to be a non-venomous African brown house snake, measuring at least three feet long.
The woman had opened the oven door to pop in her chips when she spotted the snake - later named Sammy by the RSPCA - at her home in Stockport, Greater Manchester.
She said: "When I opened the oven door and saw it I got the shock of my life.
"I have recently had a cataract operation and was wondering if my eyes were deceiving me - but my husband saw it too.
Happy it didn’t hurt her.