Tonkatsu is a Japanese dish that consists of a breaded, deep-fried pork cutlet. It involves coating slices of pork with panko, and then frying them in oil. The two main types are fillet and loin. Tonkatsu is also the basis of other dishes such as katsukarē and katsudon.

Deep frying is a cooking method in which food is submerged in hot fat, traditionally lard but today most commonly oil, as opposed to the shallow oil used in conventional frying done in a frying pan. Normally, a deep fryer or chip pan is used for this; industrially, a pressure fryer or vacuum fryer may be used. Deep frying may also be performed using oil that is heated in a pot. Deep frying is classified as a hot-fat cooking method. Typically, deep frying foods cook quickly since oil has a high rate of heat conduction and all sides of the food are cooked simultaneously.