The fourth series of the British science fiction programme Primeval began on 1 January 2011 and concluded on 5 February 2011 after airing seven episodes. Primeval follows a team of scientists tasked with investigating the appearance of temporal anomalies across the United Kingdom through which prehistoric and futuristic creatures enter the present. Following the departures of key actors in the third series and the inability of some of the actors to return for the fourth series, several new main cast members were introduced, including Ciarán McMenamin, Ruth Kearney, Alexander Siddig and Ruth Bradley.