Mayday, known as Air Crash Investigation(s) outside of the United States and Canada and also known as Mayday: Air Disaster (The Weather Channel) or Air Disasters (Smithsonian Channel) in the United States, is a Canadian documentary television series produced by Cineflix that recounts air crashes, near-crashes, fires, hijackings, bombings, and other mainly flight-related disasters and crises. It reveals the events that led to each crisis or disaster, their causes as determined by the official investigating body or bodies, and the measures they recommended to prevent a similar incident from happening again. The programs use re-enactments, interviews, eyewitness testimony, computer-generated imagery, cockpit voice recordings, and official reports to reconstruct the sequences of events.

As of 12 January 2025, 276 episodes of Mayday have aired. This includes five Science of Disaster specials, each examining multiple crashes with similar causes. For broadcasters that do not use the series name Mayday, three Season 3 episodes were labelled as Crash Scene Investigation spin-offs, examining marine or rail disasters.

A sub-series labelled The Accident Files began airing in 2018 and, as of 2024, has aired six seasons. The first five seasons consisted of ten episodes per series and the sixth season consisted of six episodes. This sub-series consists entirely of summarized versions of air disasters previously investigated in the primary Mayday series, but combined based on similarities between the incidents, such as fires or pilot error. Each episode covers three accidents and 15 minutes is dedicated to each of the disasters that are covered.