Simmering is a food preparation technique by which foods are cooked in hot liquids kept just below the boiling point of water (lower than 100 °C or 212 °F) and above poaching temperature (higher than 71–80 °C or 160–176 °F). To create a steady simmer, a liquid is brought to a boil, then its heat source is reduced to a lower, constant intensity (smaller flame on a gas stove, lower temperature on an induction/electric stove). Visually a liquid will show a little movement without approaching a rolling boil.

Simmering ensures gentler treatment than boiling to prevent food from toughening and/or breaking up. Simmering is usually a rapid and efficient method of cooking. Food that has simmered in milk or cream instead of water is sometimes referred to as creamed. The appropriate simmering temperature is a topic of debate among chefs, with some but not all considering that a simmer is as low as 82 °C or 180 °F.

Some modern gas ranges have a simmering burner, which may be a rear burner, supporting a steady low heat. Many electric ranges have a simmer setting.

Slow cookers are countertop electrical appliances used to cook foods at simmering temperature or somewhat lower for hours at a time.

In Japanese cuisine, simmering is often considered one of the four essential cooking techniques, along with grilling, steaming, and deep frying.

Food prepared in a crockpot or slow cooker is simmered. Examples include stews, chili con carne, soups, etc.

Bulgarian traditional food, especially tender meat dishes are often simmered for extended periods of time. Examples include stews, soups, Vanyas, etc.

In traditional Dutch and Flemish cuisine, less tender cuts of beef are simmered for several hours to obtain carbonade flamande. Traditionally a small flame is used, fed by burning oil, or a very low gas flame on a cooker. A cast iron pan with a thick bottom is often used in many countries. The meat is ready if it can be easily torn apart into threads.