The snake is considered to be a least-concern species according to the International Union for Conservation of Nature, though may have declined with the spread of the cane toad.

[6] Belgian-British zoologist George Albert Boulenger described P. cupreus in 1896 from a specimen collected from the Murray River, distinguishing P. darwiniensis from P. australis by the shape of the frontal scale.

[8] Australian naturalist Donald Thomson obtained a skull of a large specimen with a wide head collected from East Alligator River in Arnhem Land in 1914, naming it Pseudechis platycephalus in 1933.

He distinguished it from P. australis on the basis of it having anteriorly grooved palatine and pterygoid teeth, and having blunt ridges and keels on the dorsal scales.

[9] In 1955, Australian herpetologist Roy Mackay concluded that several species previously described were synonymous with P. australis, recognising that it was a highly variable taxon.

He noted that P. australis had frontal scales of variable shape, and that grooves were present on the teeth of many specimens of Pseudechis, so these features did not support separate species.

[10] Australian herpetologists Richard W. Wells and C. Ross Wellington described Cannia centralis in 1985 from a 1.3 m (4 ft 3 in) specimen collected 8 km (5 mi) north of Tennant Creek in 1977, distinguishing it on the basis of a narrow head;[11] however, the distinction was not supported by other authors.

[15] The species was long regarded as monotypic and highly variable until German biologist Ulrich Kuch and colleagues analysed the mitochondrial DNA of specimens across its range in 2005.

[22] The term "king brown" refers to the great size of individuals in the north and northwest of Australia, which can exceed 3 m (10 ft) in length; it is the largest and most dangerous elapid of those regions.

[25] The king brown snake is robust, with a head slightly wider than the body, prominent cheeks and small eyes with red-brown irises,[25] and a dark tongue.

[25] In Western Australia, king brown snakes south of a line through Jurien Bay, Badgingarra, New Norcia, and Quairading are significantly darker in colour.

[19] King brown snakes are habitat generalists,[24] inhabiting woodlands, hummock grasslands, chenopod scrublands, and gibber or sandy deserts nearly devoid of vegetation.

[24] They are often observed at modified habitats such as wheat fields, rubbish piles, and vacated buildings; individuals may become trapped in mine shafts and wellbores.

[23] Fieldwork near Alice Springs showed that they prefer areas with buffel grass (Cenchrus ciliaris), a common introduced weed in Central Australia, possibly because of the dense, year-round cover it provides.

[33] The king brown snake is mostly crepuscular—active at dusk,[31] and is less active during the middle of the day and between midnight and dawn, retiring to crevices in the soil, old animal burrows, or under rocks or logs.

Mating follows—in the early Southern Hemisphere spring in southwest Western Australia, mid-spring in the Eyre Peninsula, and with the wet season in the north of the country.

[42] The last recorded death occurred in 1969,[43] when a 20-year-old man was bitten while reaching around for a packet of cigarettes under his bed in Three Springs, Western Australia.

[43] He reported later that he had impulsively decided to commit suicide by placing his hand in a bag with a king brown snake inside and stirring it up.

[48] This record was broken in 2016, when a king brown snake named "Chewie"—also 2.5 m (8 ft 2 in) long—produced 1500 mg of venom at the Australian Reptile Park.

[53] The main toxic agents of king brown snake venom are myotoxins hazardous to striated muscles and kidney cells.

Nonspecific symptoms of poisoning are common and include nausea and vomiting, abdominal pain, diarrhea, generalized sweating (diaphoresis), and headache.

Impaired clotting (coagulopathy) is common, and can be diagnosed with an elevated activated partial thromboplastin time (aPTT).

King brown snake venom has some haemolytic activity, and some patients get a short-term fall in red blood cells.

[55] Pseudechetoxin and pseudecin are two proteins that block cyclic nucleotide–gated ion channels, including those present in retinal photoreceptors and olfactory receptor neurons.

Christopher Johnston and colleagues propose giving antivenom immediately if king brown snake envenoming is suspected, as a delay of more than two hours did not prevent muscle damage in a review of treated snakebite victims.

They add that it is reasonable to assume that if a snakebite victim had a raised aPTT and signs of haemolysis, then a king brown snake is the culprit.

[25] Mutitjulu Waterhole at Uluru marks the site of the battle between two Central Australian ancestral beings Kuniya (woma python woman) and Liru (king brown snake man).

[59] Known as darrpa to indigenous people of East Arnhem land, the king brown snake was historically responsible for deaths there.

[61] The Kurulk clan would not collect white paint from a site in the wet season, as they believed it was the snake's faeces, and they were afraid of its anger.

Here the King Brown Snake Ancestral Being—balngarrangarra in Gudanji and ngulwa in Yanyuwa—was sleeping about 1.5 km (0.93 mi) north of the lagoon when it was disturbed by ngabaya—ancestral spirit men.