PARIS, France, Oct 19, 2026 - The European Space Agency's Euclid space telescope has discovered its first previously unknown comet, designated C/2026 S1 (Euclid).^[1] The comet was identified in imagery captured by the observatory between 16 and 24 September 2026.^[2] Euclid was originally engineered to take stable long-exposure images of distant galaxies. It was not designed, programmed or tasked to detect moving solar system objects.^[3] Mission scientists had expected Euclid would discover almost no comets over its full operational lifespan. Bruno Altieri of the Euclid archive team described the detection as a fortunate coincidence of the comet's orbit and the telescope's scan pattern.^[4] This find demonstrates the observatory can detect uncharted comets while they are still very far from the Sun.^[5] Impact Insight. Comets are primitive icy remnants from the formation of the solar system. Most are only detected once they approach close enough to the Sun to warm, outgas and brighten. Locating these objects while still distant extends the time available to map their orbits and evaluate any future Earth approach risk. This unplanned capability adds an unanticipated planetary defence utility to the cosmology mission.