Kosher foods are foods that conform to the Jewish dietary regulations of kashrut (dietary law). The laws of kashrut apply to food derived from living creatures and kosher foods are restricted to certain types of mammals, birds and fish meeting specific criteria; the flesh of any animals that do not meet these criteria is forbidden by the dietary laws. Furthermore, kosher mammals and birds must be slaughtered according to a process known as shechita and their blood may never be consumed and must be removed from the meat by a process of salting and soaking in water for the meat to be permissible for use. All plant-based products, including fruits, vegetables, grains, herbs and spices, are intrinsically kosher, although certain produce grown in the Land of Israel is subjected to other requirements, such as tithing, before it may be consumed.

Kosher food also distinguishes between meat and dairy products. Meat products are those that comprise or contain kosher meat, such as beef, lamb or venison, kosher poultry such as chicken, goose, duck or turkey, or derivatives of meat, such as animal gelatin; non-animal products that are processed on equipment used for meat or meat-derived products are also considered to belong to this category. Dairy products are those which contain milk or any derivatives such as butter or cheese; non-dairy products that are processed on equipment used for milk or milk-derived products are also considered as belonging to this category. Because of this categorization, meat and milk or their respective derivatives are not combined in kosher foods, and separate equipment for the storage and preparation of meat-based and dairy-based foods is used in order for food to be considered kosher.

Another category of kosher food, called pareve contains neither meat, milk nor their derivatives; they include foods such as fish, eggs from permitted birds, produce, grains, fruit and other edible plants. They remain pareve if they are not mixed with or processed using equipment that is used for any meat or dairy products.

Because of the complexities of modern food manufacturing, kashrut agencies supervise or inspect the production of kosher foods and provide a certification called a hechsher to verify for kosher food consumers that it has been produced in accordance with Jewish law.

Jewish dietary law is primarily derived from Leviticus 11 and Deuteronomy 14:1-21. Foods that may be consumed according to Jewish religious law are termed kosher () in English, from the Ashkenazi pronunciation of the Hebrew term kashér (כָּשֵׁר‎), meaning "fit" (in this context, fit for consumption). Foods that are not in accordance with Jewish law are called treif (; Yiddish: טרײף, derived from Hebrew: טְרֵפָה trāfáh) meaning "torn."