The Max Headroom signal hijacking occurred on the night of November 22, 1987, when the television broadcasts of two stations in Chicago, Illinois, United States, were hijacked in an act of broadcast piracy by a video of an unidentified person wearing a Max Headroom mask and costume, accompanied by distorted audio and a corrugated metal panel swiveling in the background to mimic Max Headroom's geometric background effect.The first incident took place during the sports segment of independent TV station WGN-TV's 9:00 p.m. newscast and lasted about 25 seconds. During this intrusion, the person in the mask swayed erratically and was accompanied by a strange buzzing noise. The second incident occurred around two hours later during PBS member station WTTW's broadcast of Doctor Who and lasted for about 90 seconds. The masked person spoke throughout this intrusion and made references to Max Headroom's endorsement of Coca-Cola, the TV series Clutch Cargo, WGN anchor Chuck Swirsky; and "all the greatest world newspaper nerds", a reference to WGN's call letters, which stand for "World's Greatest Newspaper". The video ended with the person's exposed buttocks being spanked by a woman with a flyswatter before normal programming resumed.

Despite an FCC investigation and decades of speculation, the culprits were never caught and have not been positively identified.