Robert Pugh was born on 3 November 1948 in Tyntetown, near Mountain Ash in the Cynon Valley, South Wales. He attended Ynysboeth school and was raised largely by his grandmother in Tynte, with family roots in nearby Cilfynydd, close to Pontypridd. He decided to become an actor after watching From Russia with Love at a cinema in Treforest, and after taking night courses at the Mountview Academy of Theatre Arts in London he won a place at Rose Bruford College, graduating in 1976.
Pugh built a long and varied screen career across British television and film, becoming known for bringing real historical figures to life, including Harold Wilson in Channel 4's Longford (2005) and Hermann Göring in the BBC drama-documentary Nuremberg: Nazis on Trial (2006). He has often returned to explicitly Welsh roles, playing Edgar Evans in the 1984 television film Terra Nova, appearing in Karl Francis's Welsh-language film Milwr Bychan (1987), and portraying the medieval Welsh prince Owain Glyndŵr in the BBC's 2012 adaptation of Henry IV, Part I.
He reached a new international audience as the wildling Craster in HBO's Game of Thrones (2012-2013), and went on to appear in The White Queen (2013), Doctor Foster (2015), Mr Selfridge (2016) and Vanity Fair (2018), among many other credits. His film work has included Master and Commander: The Far Side of the World (2003) and Kingdom of Heaven (2005).
Pugh has continued working steadily into the 2020s, returning to BBC's Casualty — the series in which he first appeared as a paramedic in the 1980s — in a recurring role in 2023, and narrating the popular BBC series The Repair Shop.