Police said it happened in the South Austin neighborhood's 5000-block of West Madison Street around 10:35 p.m.
A 29-year-old man was fighting with two other people, a male and a female of unknown ages, outside, police said.
Police said that's when the female took out a sharp object and struck the man's head before fleeing the scene.
The man was transported to Loretto Hospital, where he is listed in serious condition.
There is no one in custody, and Area Four detectives are investigating.
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