Stephen Gallagher is an English writer.

He has written several novels and television scripts, including for the BBC television series Doctor Who -- for which he wrote two serials, Warriors' Gate (1981) and Terminus (1983) -- as well as for the series Rosemary & Thyme and Bugs, for two seasons of which he was script consultant along with Brian Clemens. He adapted his own novel Chimera for ITV and directed the adaptation of Oktober as well as writing the feature-length episode The Kingdom of Bones for the BBC series Murder Rooms.

He also developed and wrote a science-based series for ITV, Eleventh Hour, starring Patrick Stewart as a government science investigator and advisor. The program was rumoured to be ITV's answer to the new series of Doctor Who, but was more in the tradition of the hard-science thriller. Gallagher's series format has been acquired for a US television remake by the CSI trio of CBS, Jerry Bruckheimer TV and director Danny Cannon.

Life Line, broadcast in 2007, was a two-part a supernatural mystery starring Ray Stevenson, Joanne Whalley and Jemima Rooper.

Stephen Gallagher is currently lead writer and story supervisor on NBC's 13-part series Crusoe, for screening in 2008/2009.