Chestnut (ee), also known as sorrel and red, is one of the base colors. Ponies are black, chestnut, bay, or brown with other colors diluting/modifying the base color. Extension and agouti form the basis of all equine color. Extension determines whether or not a pony has black or not and agouti determines where it will go. Recessive extension creates the chestnut or red color. Chestnuts carry agouti but without the dominant form of extension producing black agouti has no effect. The agouti status of chestnuts cannot be determined visually and must be tested.

Chestnut is a recessive so a pony must have two copies of chestnut in order to be chestnut. Two chestnut ponies cannot produce anything but chestnut offspring.

Flaxen chestnuts have manes and/or tails that are lighter than their body color. Other chestnuts have manes and tails that are darker than their body color. These chestnuts are referred to as tostado chestnuts.

Chestnut is likely an original color in Chincoteagues as it is widespread and the breed was originally all solid dark colors. A 1891 article in the New York City newspaper The Sun stated that the ponies "are most frequently black, gray, sorrel, or dun [buckskin]." Leonard D. Sale wrote in 1896 in The Horse Review of Chicago that, "The prevailing colors are bay, brown, chestnut and light sorrel. A 1912 Baltimore Sun article stated that the ponies were sometimes "a dull mahogany red". A 1923 St. Petersburg Times article described the ponies as "bay, gray, dun [buckskin], black, and sorrel".

Chestnut in summer and winter coat. Phantom Mist, 2007 and 2016, Picture by Amanda Geci.

Dark chestnut tobiano. Archer's Gambit, Picture by Amanda Geci.

Solid chestnut. Feral Maryland pony, Picture from The Chincoteague Pony by Charlotte Wilcox.

Chestnut tobiano splashed white as an adult and as a foal. Misty's Heart of the Storm, Adult picture by Matt DesJardins, Foal picture by Amanda Geci.

Dark chestnut splashed white. Daughter of Surfer Dude. Surfer Dude's Gidget, Pictures by Amanda Geci.

Solid chestnut. Ginger of Assateague, Picture courtesy of the National Chincoteague Pony Association.

Chestnut as a foal and as an adult. Both parents are bays. Kayak Wave Runner, 2007 foal picture by Amanda Geci, 2010 adult picture courtesy of Barbara Steele.

Solid dark chestnut. Wild Bill, 2014, Picture by Amanda Geci.

Light chestnut tobiano splashed white in summer coat and winter coat. Butterfly Kisses, 2010 and 2017, Picture by Amanda Geci.

Chestnut tobiano. Leonard Stud, Picture by Amanda Geci.

Dark tostado chestnut. His dam and sister were also dark chestnuts. Rainy's Boy, 2007, Picture by Amanda Geci.

Dark chestnut. Unforgettable, 2014, Picture by Amanda Geci.

Chestnut foal coat. Wild foal, 2007, Picture by Amanda Geci.

Solid chestnut as a foal and as an adult. Both of her parents are black tobianos. Misty's Red Dawn, 2011 and 2014, Foal picture by Amanda Geci, Adult picture by Matt DesJardins.

Dark sooty chestnut in summer and winter coats. TSG's Elusive Star, Picture by Amanda Geci.

Chestnut tobianos. Cherokee Chief and Rapt in Paint, 2003, Photo by Amanda Geci.

Herd with chestnuts. Photo from an old postcard.