The Doomsday Clock is a symbol that represents the likelihood of a human-made global catastrophe, in the opinion of the members of the Bulletin of the Atomic Scientists. Maintained since 1947, the clock is a metaphor for threats to humanity from unchecked scientific and technological advances. A hypothetical global catastrophe is represented by midnight on the clock, with the Bulletin's opinion on how close the world is to one represented by a certain number of minutes or seconds to midnight, assessed in January of each year. The main factors influencing the clock are nuclear risk and climate change. The Bulletin's Science and Security Board monitors new developments in the life sciences and technology that could inflict irrevocable harm to humanity.

The clock's original setting in 1947 was seven minutes to midnight. It has since been set backward eight times and forward 17 times for a total of 25. The farthest time from midnight was 17 minutes in 1991, and the nearest is 90 seconds, set on January 24, 2023.

The clock was moved to two and a half minutes in 2017, then forward to two minutes to midnight in January 2018, and left unchanged in 2019. In January 2020, it was moved forward to 100 seconds (1 minute, 40 seconds) before midnight. The clock's setting was left unchanged in 2021 and 2022. In January 2023, it was moved forward to 90 seconds (1 minute, 30 seconds) before midnight. Since 2010, the clock has been moved forward four minutes and thirty seconds, and has changed by five minutes and thirty seconds since 1947.