aka NGC 5272 is a globular cluster of stars in the northern constellation of Canes Venatici.
It was discovered on May 3, 1764, and was the first Messier object to be discovered by Charles Messier himself.

Many amateur astronomers consider it one of the finest northern globular clusters, following only Messier 13. M3 has an apparent magnitude of 6.2,
making it a difficult naked eye target even with dark conditions.
With a moderate-sized telescope, the cluster is fully defined.
It can be found by looking almost exactly halfway along the north-west line that would join Arcturus to Cor Caroli .
Using a telescope with a 25 cm aperture, the cluster has a bright core with a diameter of about 6 arcminutes and spans a total of double that.

This cluster is one of the largest and brightest, and is made up of around 500,000 stars.
It is estimated to be 11.4 billion years old. It is centred about 33,900 light-years away from Earth.