Hinterland — Y Gwyll (Welsh for 'the dusk') in the original Welsh language version — is a Welsh noir police procedural series broadcast on S4C in Welsh. The main character, DCI Tom Mathias, is played by Richard Harrington. On 27 November 2013, a second series was announced by S4C. The English-language version, with brief passages of Welsh dialogue, aired on BBC One Wales. When it was shown on the BBC in 2014, it was the first BBC television drama with dialogue in both English and Welsh. A third series of the show began filming in January 2016 and debuted on S4C on 30 October.

The programme is set in Aberystwyth, Ceredigion, Wales, and the three series were filmed in and around the town, often in rural locations.

The critical reaction to Hinterland was favourable. Wales Arts Review wrote: "Y Gwyll has been shot with real intelligence; simple, subtle and with both eyes focused on the feeding of the atmospheric cloud over the piece."

Hinterland went on to be shown in 150 countries.