NGC 5694 (also known as Caldwell 66) is a globular cluster in the constellation Hydra.

It was discovered in 1784 by William Herschel.

This globular cluster is located at a distance of 114,000 light-years (35,000 pc) from the Sun and 96,000 light-years (29,000 pc) from the Galactic Center[4] and is one of the oldest known globular clusters in the Milky Way Galaxy, forming nearly 12 billion years ago.

[5] Its chemical composition is highly peculiar, being highly (to nearly solar levels) enriched in alpha elements, suggesting an extragalactic origin before being captured by the Milky Way.

[6] NGC 5694 is located below the tail of the former constellation Noctua, which included faint stars within the modern IAU borders of Libra, Hydra, and Virgo.