The circulatory system (or cardiovascular system) is an organ system that moves nutrients, gases, and wastes to and from cells, helps fight diseases and helps stabilize body temperature and pH to maintain homeostasis. While humans, as well as other vertebrates, have a closed circulatory system (meaning that the blood never leaves the network of arteries, veins and capillaries), some invertebrate groups have open circulatory system. The most primitive animal phyla lack circulatory systems.

The Circulatory System is a psychedelic rock musical ensemble formed by musician/painter Will Cullen Hart, and featuring Hannah Jones, Derek Almstead, Peter Erchick, John Fernandes, and Heather McIntosh.

Hart is famous for his work in the Elephant Six Collective as one of the lead players in the The Olivia Tremor Control. After the band disbanded in 2000, he and most of the other former Olivias formed Circulatory System, with the exceptions of Bill Doss, who was focusing on his solo project Sunshine Fix, and Eric Harris. Neutral Milk Hotel's Jeff Mangum also contributed to their debut album, but was only briefly part of the touring version of the band.

A second full-length album was anticipated in early 2007, according to the label's website (see External Links), but has since been postponed indefinitely.