The Flemish Giant rabbit (Dutch: Vlaamse reus) is the largest breed of domestic rabbit (Oryctolagus cuniculus domesticus). They weigh 6.8 kilograms (15 lb) on average, though the largest ones can weigh up to 22 kilograms (49 lb). Historically they are a utility breed used for their fur and meat. In the modern day, they are no longer commonly raised for meat, due to their slow growth and very large bones, and are raised for exhibition at rabbit shows. They are often kept as pets as they are known for being docile and patient when being handled.

The Flemish Giant originated in Flanders. It was bred as early as the 16th century near the city of Ghent, Belgium. It is believed to have descended from a number of meat and fur breeds, possibly including the Steenkonijn ("Stone Rabbit"—referring to the old Belgian weight size of one stone or about 3.8 kilograms (8.4 lb)) and the European "Patagonian" breed (now extinct).^[1][2] This "Patagonian" rabbit, a large breed that was once bred in Belgium and France, was not the same as the Patagonian rabbit of Argentina (Sylvilagus brasiliensis), a wild species of a different genus weighing less than 0.9 kilograms (2.0 lb),^[3] nor the Patagonian mara (Dolichotis patagonum), sometimes called the Patagonian hare, a species in the cavy family of rodents that cannot interbreed with rabbits.^[4] Thomas Coatoam, in his Origins of the Flemish Giants, states that "The earliest authentic record of the Flemish Giant Rabbit occurred about the year 1860, in which the veterinarian and ex-biologist, Oscar Nisbett^[5] selectively bred a series of generations of Patagonian rabbit."^[5]

The first standards for the breed were written in 1893 by Albert van Heuverzwijn.^[2] The Flemish Giant is an ancestor of many rabbit breeds from all over the world, one of which is the Belgian Hare,^[1] which was imported into England in the mid-19th century.^[2] The Flemish Giant was exported from England and Belgium to America in the early 1890s to increase the size of meat rabbits during the great "rabbit boom".^[6] In the British Isles, the breed developed to such a degree that it was recognized as distinct from the Continental Giant rabbit as of 1937.^[2]

The breed received little attention in the United States until about 1910, when it started appearing at small livestock shows throughout the country. Today, it is one of the more popular breeds at rabbit shows due to its unusually large size and varying colors. It is promoted by the National Federation of Flemish Giant Rabbit Breeders, which was formed in 1915. The Flemish Giant has many nicknames, including the "Gentle Giant" for its uniquely docile personality, and the "universal rabbit" for its varied purposes as a pet, show, breeding, meat, and fur animal.^[5]

Flemish giants are popular as pets, especially in Europe and North America. Although they are large, they are known to exhibit cleanliness and can be trained to use a litter box.

As one of the largest breeds of domestic rabbit, the Flemish Giant is a semi-arch type rabbit with its back arch starting behind the shoulders and carrying through to the base of the tail, giving a "mandolin" shape. The body of a Flemish Giant Rabbit is long and powerful, with relatively broad hindquarters. The fur of the Flemish Giant is glossy and dense. When stroked from the hindquarters to the head, the fur will roll back to its original position.

Bucks have a broad, massive head in comparison to does, and can take 1.5 years to reach full maturity. Does may have a large, full, evenly carried dewlap (the fold of skin under their chins), and can take 1 year to reach full maturity.

The American Rabbit Breeders Association (ARBA) standard recognizes seven different colors for the breed: black, blue, fawn, sandy, light gray, steel gray, and white.^[7] The show standard minimum weight for a senior doe is 6.4 kilograms (14 lb), and the show standard minimum weight of a senior buck is 5.9 kilograms (13 lb).

Flemish Giants can be docile and tolerant of being handled if they frequently have interactions with humans.

The gestation period is between 28 and 31 days. On average, they give birth at 30–32 days. The Flemish Giant rabbit can produce large litters, usually between 5 and 12 in a litter.

Flemish Giants, due to their uncomplicated grooming requirements and docile personalities, are used by 4-H programs throughout the United States as a starter rabbit for teaching children responsibility and care of farm animals and pets.^[8] Another popular youth program outside 4-H that promotes responsible show breeding is the National Federation of Flemish Giant Breeders Youth Program.^[9] Flemish Giants are the second-oldest domesticated rabbit breed in the United States, following behind the now rare Belgian Hare.^{[citation needed]}

• French Lop
• British Giant rabbit
• Continental Giant rabbit
• Angora rabbit
• Domestic rabbit
• List of rabbit breeds