The European Herring Gull (Larus argentatus) is a large gull (up to 26 inches or 66 cm long), and is the most abundant and best known of all gulls along the shores of western Europe. It breeds across Northern Europe, Western Europe, Scandinavia and the Baltic states. Some European Herring Gulls, especially those resident in colder areas, migrate further south in winter, but many are permanent residents, e.g. in the British Isles, Iceland, or on the North Sea shores. European Herring Gulls are also abundant around inland garbage dumps, and some have even adapted to life in inland cities.

The male European Herring Gull is 60–66 cm (24–26 in) long and weighs 1050-1250 grams (2.3-2.8 lb) while the female is 55–62 cm (22-24.5 in) and weighs 800-980 grams (1.8-2.2 lb). The wingspan is 137–150 cm (54–59 in). Adults in breeding plumage have a grey back and upperwings and white head and underparts. The wingtips are black with white spots known as "mirrors" . The bill is yellow with a red spot and there is a ring of bare yellow skin around the pale eye. The legs are normally pink at all ages but can be yellowish, particularly in the Baltic population which was formerly regarded as a separate subspecies "L. a. omissus". Non-breeding adults have brown streaks on the head and neck. Male and female plumage is identical at all stages of development, however adult males are often larger.

Juvenile and first-winter birds are mainly brown with darker streaks and have a dark bill and eyes. Second-winter birds have a whiter head and underparts with less streaking and the back is grey. Third-winter individuals are similar to adults but retain some of the features of immature birds such as brown feathers in the wings and dark markings on the bill. The European Herring Gull attains adult plumage and reaches sexual maturity at an average age of four years.

Adult European Herring Gulls are similar to Ring-billed Gulls but are much larger, have pinkish legs, and a much thicker yellow bill with more pronounced gonys. First-winter European Herring Gulls are much browner, but second and third-winter birds can be confusing since soft part colors are variable and third-year Herring Gull often show a ring around the bill. Such birds are most easily distinguished by the larger size and larger bill of European Herring Gull.

The European Herring Gull can be differentiated from the closely-related, similarly sized and proportioned Lesser Black-backed Gull by the latter's dark grey (not actually black) back and upperwing plumage and its yellow legs and feet.

The loud laughing call is well-known in the northern hemisphere. The European Herring Gull also has a yelping alarm call and a low barking anxiety call.

European Herring Gull chicks and fledglings emit a distinctive, repetitive high-pitched 'peep', accompanied by a head-flicking gesture when begging for food from, or calling to their parents. It should also be noted that adult gulls in urban areas will also exhibit this behaviour when fed by humans.

European Herring Gull flocks have a loose pecking order, based on size, aggressiveness and physical strength. Adult males are usually dominant over females and juveniles in feeding and boundary disputes, whilst adult females are typically dominant when selecting nest sites. Communication between these birds is complex and highly-developed — employing both calls and body language. Two identical vocalizations can have very different (sometimes opposite) meanings, for example — depending on the positioning of the head, body, wings and tail relative to each other and the ground in the calling gull.

Unlike many flocking birds, European Herring Gulls do not engage in social grooming and keep physical contact between individuals to a minimum. Outside of the male/female and parent/chick relationship, each gull attempts to maintain a respectful 'safe distance' from others of its kind. Any breach of this results in fighting, though severe injuries are seldom inflicted.

European Herring Gulls are known to be capable of seeing ultraviolet light.

These are omnivores and opportunists like most Larus gulls, and will scavenge from garbage dumps, landfill sites, and sewage outflows, with refuse comprising up to half of the bird's diet. It also steals the eggs and young of other birds (including those of other gulls), as well as seeking suitable small prey in fields, on the coast or in urban areas, or robbing plovers or lapwings of their catches. European Herring Gulls may also dive from the surface of the water or engage in plunge diving in the pursuit of aquatic prey, though they are typically unable to reach depths of greater than 1–2 metres due to their natural buoyancy. Despite their name, they have no special preference for herrings — in fact, examinations have shown that echinoderms and crustaceans comprised a greater portion of these gulls' stomach contents than fish, although fish is the principal element of regurgitations for nestlings. European Herring Gulls can frequently be seen to drop shelled prey from a height in order to break the shell. In addition, the European Herring Gull has been observed using pieces of bread as bait with which to catch goldfish. Vegetable matter such as roots, tubers, seeds, grains, nuts and fruit is also taken to an extent.

European Herring Gulls may be observed rhythmically drumming their feet upon the ground for prolonged periods of time in a behaviour that superficially resembles Irish stepdancing. This is for the purpose of creating vibrations in the soil, driving earthworms to the surface, which are then consumed by the gull. It is believed that these vibrations mimic those of digging moles, eliciting a surface escape behaviour from the earthworm, beneficial in encounters with this particular predator, which the European Herring Gull then exploits to its own benefit in a similar manner to human worm charmers.

Whilst the European Herring Gull is fully capable (unlike humans) of consuming seawater, utilizing specialized glands located above the eyes to remove excess salt from the body (which is then excreted in solution through the nostrils and drips from the end of the bill), it will drink fresh water in preference, if available.

During courtship, the hen will approach the cock on his own territory with a hunched, submissive posture whilst making begging calls (similar to those emitted by young gulls). If the cock chooses not to attack her and drive her away, he will respond by assuming an upright posture and making a mewing call. This is followed by a period of synchronised head-tossing movements, after which the cock will then regurgitate some food for his prospective mate. If this is accepted, copulation will follow. A nesting site will then be chosen by both birds. European Herring Gulls are almost exclusively sexually monogamous and may pair up for life, provided that the couple are successful in hatching their eggs.

Two to four eggs, usually three, are laid on the ground or cliff ledges in colonies, and are defended vigorously by this large gull. The eggs are a dark blotched, olive color. They are incubated for 28–30 days. Breeding colonies are predated by great black-backed gulls, harriers, corvids, herons and raccoons.

Juveniles use their beaks to "knock" on the red spot on the beaks of adults to indicate hunger. Parents typically disgorge food for their offspring when they are "knocked". The young birds are able to fly 35–40 days after hatching and fledge at six weeks of age. Chicks are generally fed by their parents until they are 11–12 weeks old but the feeding may continue up to six months of age, if the young gull continues to beg. The male feeds the chick more often than the female before fledging, the female more often post-fledging. Like most gulls, European Herring Gulls are long lived, with a maximum age of 49 years recorded. Raptors (especially owls, peregrine falcons and gyrfalcons) and seals (especially grey seals) occasionally prey on the non-nesting adults.