In animal husbandry, a concentrated animal feeding operation (CAFO; popularly known as factory farm), as defined by the United States Department of Agriculture (USDA), is an intensive animal feeding operation (AFO) in which over 1,000 animal units are confined for over 45 days a year. An animal unit is the equivalent of 1,000 pounds of "live" animal weight. A thousand animal units equates to 700 dairy cows, 1,000 meat cows, 2,500 pigs weighing more than 55 pounds (25 kg), 10,000 pigs weighing under 55 pounds, 10,000 sheep, 55,000 turkeys, 125,000 chickens, or 82,000 egg laying hens or pullets.

CAFOs are governed by regulations that restrict how much waste can be distributed and the quality of the waste materials. As of 2012 there were around 212,000 AFOs in the United States,^: 1.2 19,496 of which were CAFOs.

Livestock production has become increasingly dominated by CAFOs in the United States and other parts of the world. Most poultry was raised in CAFOs starting in the 1950s, and most cattle and pigs by the 1970s and 1980s. By the mid-2000s CAFOs dominated livestock and poultry production in the United States, and the scope of their market share is steadily increasing. In 1966, it took 1 million farms to house 57 million pigs; by 2001, it took only 80,000 farms to house the same number.