"Silence in the Library" is the eighth episode of the fourth series of the British science fiction television series Doctor Who. It was first broadcast on 31 May 2008 on the British Broadcasting Corporation (BBC). It is the first of a two-part story, followed by "Forest of the Dead", and is the second two-parter Steven Moffat contributed to the series after "The Empty Child" and "The Doctor Dances" from the first series.

In the episode, the Doctor—a Time Lord played by David Tennant—and his companion Donna Noble (Catherine Tate) land in the 51st century to visit the greatest library in the universe, encompassing an entire planet, but are baffled when they find it deserted. To the best he can determine, the library has been closed for 100 years so the arrival of a team of archaeologists led by River Song (Alex Kingston), comes as something of a surprise. They discover the Vashta Nerada, carnivorous creatures living in the shadows, are responsible. All they have is one warning—count the shadows.

The Hugo Award-nominated episode is also significant for introducing the character of River Song, who would go on to play an important role in future stories. A few days before the episode aired, the BBC announced that Moffat was to become head writer of the programme for the show's fifth series in 2010, replacing then-current head writer Russell T Davies, who held the role since Doctor Who returned to television in 2005.

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