The Boulonnais, also known as the "White Marble Horse", is a heavy draft horse breed. It is known for its large but elegant appearance and is usually gray, although chestnut and black are also allowed by the French breed registry. Originally there were several sub-types, but they were crossbred until only one is seen today. The breed's origins trace to a period before the Crusades and, during the 17th century, Spanish Barb, Arabian and Andalusian blood was added to create the modern type.
During the early 1900s, the Boulonnais were imported in large numbers to the United States and were quite popular in France; however, the European population suffered severe decreases during 20th century wars. The breed nearly became extinct following World War II, but rebounded in France in the 1970s as a popular breed for horse meat. Breed numbers remain low, with an estimation of less than 1,000 horses remaining in Europe, mostly in France with a few in other nations. Studies as early as 1983 indicated a danger of inbreeding within the Boulonnais population, and a 2009 report suggested that the breed should be a priority for conservation within France. The smallest type of Boulonnais was originally used to pull carts full of fresh fish from Boulogne to Paris, while the larger varieties performed heavy draft work, both on farms and in the cities. The Boulonnais was also crossbred to create and refine several other draft breeds.