Torchwood: Miracle Day is the fourth series of the British science fiction television series Torchwood, a spin-off from the long-running show Doctor Who. In contrast to the first three series, which were produced by the BBC, the fourth series is a British-American co-production involving the BBC's drama production house BBC Cymru Wales for BBC Worldwide and the U.S. premium network Starz. It was broadcast in ten episodes beginning 8 July 2011 (U.S.) and 14 July 2011 (UK).
The central plot of Miracle Day is that suddenly no one on Earth can die, which incites increasingly troublesome legislative changes around the world as the global population soars. In addition to a number of new American cast members and guest actors, showrunner Russell T Davies recruited several American television writers to write for Miracle Day, including Jane Espenson, John Shiban and Doris Egan. British writer John Fay also returned to write for the series, under Davies as head writer. Production was partially divided along trans-Atlantic lines, with Kelly Manners producing in the US, and Brian Minchin in the UK. The majority of the filming took place in Los Angeles, California, with two weeks' additional shooting in Wales.