Its legs, which have unique daffodil-yellow markings, span a massive 20cm (eight inches). The arachnid also has a distinctive pink band around its body.
The new species was found in the war-torn north of the South Asian country by scientists from Sri Lanka’s Biodiversity Education and Research (BER) organisation.
It has been named Poecilotheria rajaei, in recognition of a senior police officer called Michael Rajakumar Purajah, who guided the research team through a hazardous jungle overrun by civil unrest in order to seek out the spider.
The arachnid had originally been presented to BER three years ago by villagers in Mankulam, who had killed a male specimen.
Scientists immediately realised the dead spider was not like anything they already knew and a group was charged with finding any living relatives.
The living Poecilotheria rajaei were eventually discovered in the former doctor’s quarters of the village’s hospital.
According to wired.com, Ranil Nanayakkara, the co-founder of BER, said: “They are quite rare.
“They prefer well-established old trees, but due to deforestation the number have dwindled and due to lack of suitable habitat they enter old buildings.”
The website described the tarantula as “colourful, fast and venomous”.
The species is said to be related to a class of South American tarantula that includes the Goliath bird-eater, one of the world’s largest spiders.
In other reports Mr Nanayakkara is quoted as saying none of the tarantulas found in Sri Lanka have bites that are deadly to humans. However, the Poecilotheria rajaei would be able to kill animals as large as mice, lizards and small birds and snakes.
Peter Kirk, who covered the discovery for the British Tarantula Society’s journal, told Sky News: “Ranil has been working on these spiders since 2009 out in Sri Lanka and this is the first of what is thought to be a number of new species he has discovered in what was previously the inaccessible northern region of the island.
“It demonstrates that wildlife continues to survive whilst we are in the throes of conflict and that they can adapt to its changing environment – but also highlights that we risk destroying the habitats of species new to science and condemning them to extinction before they are even discovered.”