Mackerel is a common name applied to a number of different species of pelagic fish, mostly, but not exclusively, from the family Scombridae. They are found in both temperate and tropical seas, mostly living along the coast or offshore in the oceanic environment.

Mackerel typically have vertical stripes on their backs and deeply forked tails. Many species are restricted in their distribution ranges, and live in separate populations or fish stocks based on geography. Some stocks migrate in large schools along the coast to suitable spawning grounds, where they spawn in fairly shallow waters. After spawning they return the way they came, in smaller schools, to suitable feeding grounds often near an area of upwelling. From there they may move offshore into deeper waters and spend the winter in relative inactivity. Other stocks migrate across oceans.

Smaller mackerel are forage fish for larger predators, including larger mackerel. Flocks of seabirds, as well as whales, dolphins, sharks and schools of larger fish such as tuna and marlin follow mackerel schools and attack them in sophisticated and cooperative ways. Mackerel is high in omega-3 oils and is intensively harvested by humans. In 2009, over five millions tonnes were landed by commercial fishermen (see graph on the right). Sport fisherman value the fighting abilities of the king mackerel.