The huge bugs, which can kill with a single sting and have venom that melts human flesh, were blamed for five deaths in France last year.
There are fears the invaders have now crossed the Channel after the latest sighting in Devon.
Shocked Beverley Palfreman, 55, ran for cover after grabbing a picture of the scary stinger on the windowsill of her country home.
The mother-of-three of Sampford Chapple, nr Okehampton, Devon, said: “I was terrified. I just don’t do insects.
“I was in the lounge and we have got a wood burner and I kind of heard something in the burner.
“I didn’t pay any attention to it but then I heard a noise outside of it and saw something crawling on the window sill.
“I thought to myself, that’s huge, that must be a cockroach but it had wings.
“My phone was out and I took a video and nearly swore.”
Beverley, a retired occupational therapist, went online to identify the mystery menace, which had a yellow head and brown body with faint yellow band.
She said: “It doesn’t appear to be the European hornet, which has red head with yellow striped body.
“The one I saw was brown with a yellow head.
“I was able to see its brown velvet like body with a faint yellow band, and it’s head was yellow.
“Apparently, this species was responsible for five deaths from anaphylactic shock in France in 2015.
“They can also kill about 50 bees a day, so not a great thing for our beekeepers.”
Asian hornets are not yet officially recorded in the UK, but expansion from non-native population in South West France is a threat.
The insects are native to temperate and tropical Eastern Asia and have jaws strong enough to chew through protective bee clothing.
A single sting from the beast can kill because of the neurotoxin it contains.
They are even known to spray their venom which can MELT human flesh and are blamed for up to 40 deaths a year in Japan.