The tooth, dug up at Blick Mead in Wiltshire, is believed to be evidence of the earliest journey in British history.
It is thought to be from a pet Alsatian-type dog that travelled 250 miles from York with its owner.
Archaeologist David Jacques said it was significant as it was not known people travelled so far 7,000 years ago.
The shape and size show the tooth was from a domestic dog, he said.
It also suggests people were visiting Stonehenge 2,000 years before the monument was built.
"The fact that a dog and a group of people were coming to the area from such a long distance away further underlines just how important the place was four millennia before the circle was built," Mr Jacques said.
"Discoveries like this give us a completely new understanding of the establishment of the ritual landscape and make Stonehenge even more special than we thought we knew it was."
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Bones found near the tooth suggest the dog would have feasted on salmon, trout, pike, wild pig and red deer.
Researchers at Durham University used carbon dating to discover the age of the tooth and isotope analysis on the enamel.
Mr Jacques, a senior research fellow at the University of Buckingham, said: "We know it was probably born in the area of York.
"It was drinking from the area when it was young, it went on a journey of about 250 miles to the Stonehenge area with people and it ate what the people were eating on this site at Blick Mead.
"You would not get a wolf travelling 250 miles but you're much more likely to get a dog doing that because it's travelling with its people."
Previous excavations have uncovered tools from Wales and the Midlands and evidence people lived near Stonehenge for long periods of time, near the natural springs used hollowed out tree trunks for shelter.
A tooth unearthed near Stonehenge shows dogs were man's best friend even in prehistoric times, it has been claimed.