The Chicxulub impactor, also known as the K/Pg impactor and (more speculatively) as the Chicxulub asteroid, was an asteroid or comet at least 10 kilometres (6 miles) in diameter which struck the Earth at the end of the Cretaceous, approximately 66 million years ago, creating the Chicxulub crater. It impacted a few miles from the present-day town of Chicxulub in Mexico, after which the impactor and its crater are named. Because the estimated date of the object's impact and the Cretaceous–Paleogene boundary (K–Pg boundary) coincide, there is a scientific consensus that its impact was the Cretaceous–Paleogene extinction event which caused the death of the planet's non-avian dinosaurs and many other species.
The impactor's crater is more than 180 km (110 miles) in diameter, making it the third largest known impact crater on Earth.
Explanation from: https://en.wikipedia.org/wiki/Chicxulub_impactor