Abell 370 is a galaxy cluster located nearly 5 billion light-years away from the Earth (at redshift z = 0.375), in the constellation Cetus. Its core is made up of several hundred galaxies. It was catalogued by George Abell, and is the most distant of the clusters he catalogued.

In the 1980s astronomers of Toulouse Observatory discovered a gravitational lens in space between Earth and Abell 370 using the Canada-France-Hawaii Telescope. A curious arc had been observed earlier near the cluster, but the astronomers were able to recognize it as this phenomenon.