Under U.S. law, rye whiskey must contain at least 51% rye in its mash bill.
Rye whiskey is an American whiskey category defined by the dominant grain used before fermentation. The remaining grains commonly include corn and malted barley, which contribute sweetness, body, and enzymes needed during mashing.
The 51% threshold makes rye whiskey distinct from bourbon, whose mash must contain at least 51% corn. Rye whiskey is often associated with a spicier, drier flavor profile, although production methods, barrel aging, and recipe differences can strongly affect the final taste.
This rule applies to the grain recipe, not to the alcohol percentage in the finished bottle. Rye whiskey may be bottled at different strengths, provided it also meets other U.S. standards for distillation, maturation, and bottling.