The woman was at a bus stop on Moonshine Lane, Southey, when she was approached by a man who demanded her purse.
CRIME: Bogus police officer hunted over spate of burglaries in SheffieldWhen she refused to hand it over he pulled out and knife and threatened her.
A South Yorkshire Police spokesman said: "A lone female stood at a bus stop on Moonshine Lane was approached by a male offender.
"He engages her in conversation and demands her purse, which she refuses.
"The male then pulls out a knife and threatens the victim with violence.
"Luckily, she spots a friend close by and quickly makes her way toward them.
"The offender realises that he has failed in his attempt runs off down the road."
Anyone with information about the incident at 1pm on Tuesday should call South Yorkshire Police on 101.