The northern pike is a species of carnivorous fish of the genus Esox (the pikes). They are typical found in freshwaters throughout the northern hemisphere.

Northern pike are most often olive green, shading into yellow to white along the belly. The flank is marked with short, light bar-like spots and there are a few to many dark spots on the fins. Sometimes the fins are reddish. Younger pike have yellow stripes along a green body, later the stripes divide into light spots and the body turns from green to olive green. The lower half of the gill cover lacks scales and they have large sensory pores on their head and on the underside of the lower jaw which are part of the lateral line system. Unlike the similar-looking and closely related muskellunge, the northern pike has light markings on a dark body background and fewer than six sensory pores on the underside of each side of the lower jaw.

Pike grow to a relatively large size; lengths of 150 centimetres (59 in) and weights of 25 kilograms (55 lb) are not unheard of.

Pike are found in sluggish streams and shallow, weedy places in lakes, as well as in cold, clear, rocky waters. Pike are typical ambush predators; they lie in wait for prey, holding perfectly still for long periods and then exhibit remarkable acceleration as they strike. In short they will inhabit any water body that contains fish, but essential for their numbers are suitable places for spawning and because of their cannibalistic nature places where young pike can take shelter between plants so they are not eaten. In both cases it comes down to a rich submersible vegetation nearby. Pikes are seldom found in brackish water except for the Baltic Sea area. Pike is known to prefer water with less turbidity but probably that is related to their dependence to the presence of submersible vegetation and not to their being a sight hunter.

Pike is known to spawn very early starting in May. The males are first at the spawning grounds preceding the females for a few weeks. The larger females tend to be earlier then the smaller ones. Mostly a female is followed by several smaller males. When a pair starts slowing down the male will put his tail under the female's body and release his spawn that is mixed with the eggs due to the tail movement. The spawning consists of a great number of these moves several times a minute and going on for a few hours a day. Every move between 5 and 60 eggs are laid. A female can continue the mating for three days in a row. After the mating the males tend to stay in the area for a few extra weeks.

The color of the sticky eggs is yellow to orange, the diameter is 2.5 to 3 mm. The embryos are 7.5 to 10 mm in length and able to swim after hatching but stay on the bottom for some time. The embryonic stage is 5 to 16 days, dependent on water temperature (19 and 10 degrees respectively). Under natural circumstances the survival from free swimming larva to 75 mm pike is around 5 percent. Pike can reach the reproductive stage in a year, females being 30 cm, males 19 cm. Pike normally live 5 to 15 years, but can be as old as 30. Life expectancy and growth are dependent on circumstances. Some Canadian populations have many old slender pikes, Baltic pike grow to great lengths in a short time while eating nutrient rich herring.

The young free swimming pike feed on small invertebrates startin with daphnia, and quicky moving on to bigger prey like isopods like asellus or gammarus. When the body length is 4 to 8 cm they start feeding on small fish.

The pike have a very typical hunting behavior, they are able to remain stationary in the water, by just moving the last fin rays of the dorsal fins and the breast fins. Before striking they bend their body and dash out to the prey using the large surface of tail fin, dorsal fin and anal fin to propel themselves. The fish has a distinctive habit of catching its prey sideways in the mouth, immobilising it with its sharp backward pointing teeth, and then turning the prey headfirst to swallow it. It eats mainly fish, but on occasion water voles and ducklings have also been known to fall prey to pike. Young pike have been found dead from choking on a pike of a similar size. Northern pike also feed on frogs, insects and leeches. They are not very particular and eat spiny fish like perch and will even take sticklebacks if that is the only available prey.

The northern pike is a largely solitary predator. It migrates during a spawning season, and it follows the prey fish like roach to their deeper winter quarters. Sometimes diverse observe groups of similar sized pike that might have some coorporation and it is known to anglers pike tend to start hunting at the same time, so there are some "wolfpack" theories about that. Large pike can be caught on dead immobile fish so it is thought that these pike move about in a rather large territory to find the food to sustain them. Large pike are also known to cruise large water bodies at a few meters depth, probably pursuing schools of prey fish. Smaller pike are more of an ambush predator, probably because of their vulnerability to cannibalism. Pikes are often found near the exit of culverts, which can be attributed to the presence of schools of prey fish and the opportunity for ambush.