Mutton is meat from a sheep that is older than one year, ideally three years old. It is an intense red color and contains a considerable amount of fat. Its flavor is very strong, and it might take some time to acquire the taste before being able to enjoy a meal of mutton if youre an American. Mutton is much more popular in the Middle East and Europe than in the United States. In contrast, lamb is a sheep that is typically less than one year old. There is little fat on lamb, and the meat can vary in color from a tender pink to a pale red. Lamb less than three months of age is called spring lamb. Spring lamb is extremely tender but has a milder flavor than lamb. Most sheep meat sold in the United States comes from lambs simply because mutton doesnt have much of a following in the U.S. In general, lamb is more expensive than mutton and much easier to find in regular markets.