1I/ʻOumuamua, detected in October 2017 by the Pan-STARRS survey, was the first known interstellar object to pass through our Solar System. Its hyperbolic trajectory — excess velocity of about 26 km/s relative to the Sun — proved it originated from another star. ʻOumuamua's elongated shape (roughly 10:1 aspect ratio), lack of cometary outgassing, and an unexpected acceleration away from the Sun sparked intense debate about its nature, from hydrogen iceberg to alien artefact. It passed within 0.25 AU of Earth before receding beyond Saturn's orbit, never to return. The encounter opened the field of interstellar object studies and raised the question of how many such visitors pass unnoticed each year.