Kate Cruise O'Brien (1948 – 26 May 1998) was an Irish writer.
The third and youngest child of the politician and diplomat Conor Cruise O'Brien, she was born in Dublin, and grew up in Howth. She went to school in Dublin and studied English in Trinity College Dublin. Her mother, Christine Foster, came from Derry City.
While still at university she published her first short story and shortly afterwards, at the age of 22 she won the Hennessy Literary Award. She graduated in 1971 and married Joseph Kearney, son of a former secretary to the Department of Defence. She returned to university to study for a Higher Diploma in Education. Unable to find a teaching post she started a small nursery for the children of working mothers.
Her first book, A Gift Horse, a collection of short stories, won her the Rooney Prize for Irish Literature. Sean O'Faolain described it as containing "the seed of genius". She later became a literary editor with the Poolbeg Press, and became well known for her canny knack of uncovering new talent.