3I/ATLAS

{{Infobox comet | name = 3I/ATLAS | image = 3I-ATLAS noirlab2532b.jpg | caption = 3I/ATLAS photographed in color by the Gemini North telescope on 26 November 2025 | discovery_ref = | discovery_site = ATLAS–CHL (W68) | discovery_date = 1 July 2025 | mpc_name = C/2025 N1 | designations = A11pl3Z | orbit_ref = | barycentric = | epoch = 19 February 2026(JD 2461090.5) | observation_arc = 280 days | obs = 782 used of 7886 | earliest_precovery_date = 7 May 2025 | orbit = Hyperbolic (interstellar) | perihelion = | last_p = 29 October 202511:45 UT | max_speed = at perihelion{{efn|name=vp-formula|1=Formula for the perihelion velocity: \sqrt{-GM(2/q-1/a)}, where G is the gravitational constant, M the mass of the Sun, q the comet's perihelion distance, and a its semi-major axis. Calculation: />v =  | semimajor = | eccentricity = | inclination = °(retrograde and inclined 4.89°) | asc_node = ° | arg_peri = ° | Earth_moid = | Mars_moid = | Jupiter_moid = | physical_ref = | dimensions = | mean_diameter = | mass = | rotation = | albedo = | abs_magnitude = >15.4 | spectral_type = | M1 = | M2 = | magnitude = 18 }}

3I/ATLAS, also known as C/2025 N1 (ATLAS) and previously as A11pl3Z, is an interstellar comet discovered on 1 July 2025 by the Asteroid Terrestrial-impact Last Alert System (ATLAS) station. The comet follows an unbound, hyperbolic trajectory past the Sun, and passed by Earth at 1.8 AU, posing no threat. The prefix "3I" designates it as the third confirmed interstellar object passing through the Solar System, after 1I/Oumuamua and 2I/Borisov.