The half-kilo (1lb) ring - known to archaeologists as a torc - was found by a tractor driver ploughing a field. Decorated with eight tapering triangular motifs, it is made from a 27-inch long piece of gold, and dates from the Bronze Age. It has no exact parallel and is thought to have been made between the 13th and 11th centuries BC.
Bronze Age gold torcs are a phenomenon of the British Isles and western France. Over the past two centuries 125 have been found in 90 locations. Only one other has been found in Lincolnshire.
In England, 14 have come from Norfolk and Cambridgeshire, five from Kent, and eight from the Wessex region. Wales and Ireland have yielded 17 and 37, while 22 have come from western France.
Torcs were probably used as high-status personal adornment and possibly placed around necks of religious idols. Archaeologists at the British Museum are examining the latest find.
The tractor driver who found the torc (which is probably worth between pounds 5,000 and pounds 20,000) kept it in his greenhouse and 'scrap bucket'. But after a local jeweller offered him pounds 1,000 for the object, the driver decided to inform the authorities of the find and the treasure was subsequently shown to the county museum.
Archaeologists from the Heritage Lincolnshire organisation now plan to search the area for more gold torcs and other Bronze Age artefacts.
It is not yet known why the torc was buried in the field. It may have been put there for safe-keeping by its original owners - or it may have been an offering to the gods.
A treasure trove inquest will be held at Sleaford Coroner's Court.