She has played a highly lucrative game of Highland hide-and-seek for decades, but fears are rising that Scotland's most elusive resident may be no more.
The publication of shadowy photographs in the 1930s apparently showing a dinosaur-like creature at large in Loch Ness sparked a media frenzy that lasted for the rest of the century.
However, sightings of Nessie have plummeted in recent years, giving rise to fears that the long-necked Caledonian leviathan is either dead or ailing.
There have been only two reported sightings so far this year and there were only three in 2006. A decade ago the numbers were consistently in the high teens.
"It has become a potential crisis," admitted Mikko Takala, a founder member of the Official Loch Ness Monster Fan Club.
Even the American scientist Dr Robert Rines, who captured the famous 'flipper' image of Nessie in 1974, believes the monster is unlikely to have survived.
"There is very little vegetation left in the loch for creatures to eat," he said.
"Everything is going against these things still being there."
Steve Feltham, 44, who has spent 16 years watching the loch from a converted mobile library on its southern shore, believes there were once as many as 30 mysterious creatures in the loch, but that they are gradually dying off because of old age.
"In the heyday of the sightings, back in the Sixties and Seventies, there were probably 20 or 30 of these animals, but I believe that we're now down to the last half dozen," he said.
Nessie tourism brings in an estimated £6m a year for the economy of the Highlands. But without the publicity created by sightings, the tourist industry faces an uncertain future.
In the era of digital cameras, camera-phones and webcams, it is perhaps surprising that there have not been more reported sightings in recent years.
Of the two reported sightings this year, one was in March when an English holidaymaker saw what he thought was a head and fin in the loch below Urquhart Castle, while the other was in May, when a Yorkshireman captured video footage of what looked like a jet-black shape moving slowly beneath the surface. Although initially viewed as promising, experts now believe it was the result of a sustained draft of wind blowing from the surrounding hills.
Loch Ness Monster Feared Dead
Loch Ness Monster Feared Dead
