Miriam O'Callaghan was born and raised in Dublin. She studied law at UCD and qualified as a solicitor before beginning her career in television on ITV's This is your Life. She joined the BBC as a producer in 1987, and later became a reporter on BBC2's Newsnight .
Miriam returned to Ireland in 1993 to present RTE's business programme Marketplace, while continuing to cover Northern politics for Newsnight. In 1996 she became the presenter of RTE's flagship current affairs programme Prime Time.
In August 2000 Miriam co-founded Mint, a media company specialising in television production.
She has presented Prime Time since 1996, and her own summer Talk show, Saturday Night with Miriam, since 2005. In the summer of 2009, she began a radio show, Miriam Meets..., since replaced by live show Sunday with Miriam.
In 2003, she won the Television Personality of the Year Award at the Irish Film and Television Awards.
She was awarded an honorary Doctor of Letters (D.Litt) degree by the University of Ulster in Derry on 5 July 2011.
She has won the RTÉ Guide Style Award.