An oil spill (sometimes called an oil slick) is the unintentional release of liquid petroleum hydrocarbon into the environment as a result of human activity.
The term often refers to marine oil spills, where oil is released into the ocean or coastal waters. Oil can refer to many different materials, including crude oil, refined petroleum products (such as gasoline or diesel fuel) or by-products, ships' bunkers, oily refuse or oil mixed in waste. Oil is also released into the environment from natural geologic seeps on the seafloor, for example along the California coastline. Most man-made oil pollution comes from land-based activity, but public attention and subsequent regulation has tended to focus most sharply on seagoing oil tankers.