Lavender foal syndrome (LFS), also called coat color dilution lethal (CCDL), is an autosomal recessive genetic disease that affects newborn foals of certain Arabian horse bloodlines. Affected LFS foals have severe neurological abnormalities, cannot stand, and require euthanasia shortly after birth. The popular name originates due to a diluted color of the foals coat, that in some cases appears to have a purple or lavender hue. However, not all foals possess the lavender coat colour, colouring can range from silver to light chestnut to a pale pink. Carrier horses have no clinical signs and DNA testing can determine if a horse carries the gene.

The condition has been recognized since the mid- to late-1950s.

Research into the genetics of LFS has been conducted at the University of California, Davis and Cornell University in the United States, the University of Queensland in Australia, and the University of Pretoria in South Africa. In November, 2009, Cornell University announced a DNA test has been developed to detect carriers of LFS. Simultaneously, the University of Pretoria also announced they had developed a DNA test. Testing is now available at Cornell, Pretoria, and Queensland, Australia.