NGC 3621 is a spiral galaxy located 22 Mly away in the constellation of Hydra. It is very bright and can be well seen in moderate-sized telescopes. The galaxy is around 93,000 ly across and is at an angle of 25° from being viewed edge on.

It shines with a luminosity equal to 13 billion times that of the our Sun. This galaxy has an active nucleus that matches a Seyfert 2 optical spectrum, suggesting that a low mass supermassive black hole is present at the core. Based upon the motion of stars in the nucleus, this object may have a mass of up to three million times the mass of the Sun.