Do Not Adjust Your Set (DNAYS) is a British television series produced originally by Rediffusion, London, then, by the fledgling Thames Television for British commercial television channel ITV from 26 December 1967 to 14 May 1969. The show took its name from the message (frequently seen on the TV screen in those days) which was displayed when there was a problem with transmission.

It helped launch the careers of Denise Coffey, David Jason, Eric Idle, Terry Jones, and Michael Palin; the last three became members of the Monty Python comedy troupe soon afterwards. Although originally conceived as a children's programme, it quickly acquired a fandom amongst adults, including future Pythons John Cleese and Graham Chapman.

Satirical comedy/art/pop group The Bonzo Dog Doo-Dah Band also performed songs in each programme and frequently appeared as extras in sketches. The programme itself comprised a series of satirical sketches, often presented in a surreal, absurd and discontinuous style which anticipates Monty Python's Flying Circus, which followed five months after the last episode of DNAYS. Strange animations between sketches were crafted for the final episodes by Terry Gilliam, who soon graduated to Python with Palin, Jones and Idle – part of Gilliam's "Christmas cards" animation reappeared there in the "Joy to the World" segment.

One recurring feature of the show was Captain Fantastic, a superhero parody featuring David Jason in farcical and morbid adventures against villainess Mrs. Black (Coffey). These segments were shot entirely on location in London. The feature was so popular with the young audience that after DNAYS itself ended, Captain Fantastic briefly continued in its own capacity.

In 1968, DNAYS won an international award, the Prix Jeunesse, in Munich.