The eastern brown snake (Pseudonaja textilis), often referred to as the common brown snake, is a species of genus Pseudonaja. Adult eastern brown snakes are highly variable in colour. Whilst usually a uniform shade of brown, they can have various patterns including speckles and bands, and range from a very pale fawn colour through to black, including orange, silver, yellow and grey. Juveniles can be banded and have a black head, with a lighter band behind, a black nape, and numerous red-brown spots on the belly.

This species has an average length of 1.1–1.8 m (3.6–5.9 ft). The maximum recorded size for the species is 2.4 m (7.9 ft), although any specimen of greater than 2 m (6.6 ft) in length would be considered exceptionally large. Large eastern brown snakes are often confused with "king brown" snakes (Pseudechis australis), whose habitat they share in many areas.

The eastern brown snake is found all the way along the East coast of Australia, from the tip of Cape York, along the coasts and inland ranges of Queensland, New South Wales, Victoria and South Australia. They are also found in arid areas of the Northern Territory, the far east of the Kimberley in Western Australia and discontinuously in parts of New Guinea, specifically northern Milne Bay Province and Central Province in Papua New Guinea, and the Merauke region of Papua Province, in the Indonesian part of New Guinea. Because their mainly rodent diet, they can often be found near houses and farms.

The snake occupies a varied range of habitats from wet to dry sclerophyll forests (Eucalypt forests) and heaths of coastal ranges, through to savannah woodlands, inner grasslands and arid scrublands. It is not found in rainforests or other wet areas.

The eastern brown snake is diurnal (meaning it is active during the day). It is notorious for its speed and aggression throughout its habitats. When highly agitated, they hold their necks high, appearing in an upright S-shape. The snake usually seeks to flee when confronted, though it can be highly aggressive if provoked. This species is attracted to rural and farming areas, probably due to the large numbers of associated rodents. Such areas also normally provide shelter in the form of rubbish and other cover.

Being an opportunistic feeder, the eastern brown snake will consume almost any vertebrate animal, including frogs, lizards, birds, rodents or other snakes.

The eastern brown snake is considered to be the second most venomous terrestrial snake. The venom has a SC LD50 range of 36.5 - 53 μg/kg and consists mostly of neurotoxins (pre- & post-synaptic neurotoxins) and blood coagulants. These snakes kept at venom supply laboratories yield an average of 2-10 mg of venom per milking.

As with most venomous snakes, the volume of venom produced is largely dependent on the size of the snake. Clinically, the venom of the eastern brown snake is known to cause diarrhea, dizziness, collapse or convulsions, renal failure, paralysis and cardiac arrest. Without medical treatment, bites can be fatal. As this species tends to initiate their defence with non-fatal bites, the untreated mortality rate in most snakebite cases reported is 10–20%, which is not very high.