Extraterrestrial life is hypothetical life which may occur outside of Earth. Such life might range from simple prokaryotes (or comparable life forms) to beings with civilizations far more advanced than humanity.

Since the mid-20th century, active ongoing research has taken place to look for signs of extraterrestrial life. This encompasses a search for current and historic extraterrestrial life, and a narrower search for extraterrestrial intelligent life. Depending on the category of search, methods range from the analysis of telescope and specimen data to radios used to detect and send communication signals.

When will the first discovery of evidence of extraterrestrial life take place?

This question resolves as the date on which the first discovery of evidence of extraterrestrial life takes place. This can be evidence of past or present extraterrestrial life, and the life can be of any degree of complexity. The life must not owe its off-Earth presence to humans; e.g. sending Earth-originating life to Mars (even accidentally) does not count.

To qualify for a positive resolution, the discovery must be generally considered credible by the scientific community, as judged by Metaculus.