Ellen Grossman, 67, told ITV Daybreak she has become a Jay-Z fan since a video of her meeting the rapper went viral.
She sat beside the 99 Problems star on the New York subway while he was filming his latest music video and asked Jay-Z his name, what he did for a living and whether he was famous.
Grossman, an artist, said: "Perhaps it was lucky I didn't know quite how famous he was ... he may have even been relieved that someone in the world treated him like one human being."
The grandmother added: "He is amazing. And we talked for quite a while. He was really wonderful, I was just enjoying his company. The more I learn about him the more impressed I am."