The origins of the disease in Europe has been the cause of debate for centuries.
Experts estimate the bones, which show signs of syphilis, are aged between 1296 and 1445.
That suggests syphilis was already present in England before Columbus discovered the New World in 1492.
The sexually-transmitted disease, which can be treated with modern medicines, often led to dementia and death in earlier times.
Firmer proof
Dr Simon Mays, who led the team from the English Heritage's Centre for Archaeology, said: "This is very important discovery.
"This puts the theory that syphilis was not brought to Europe by Columbus on a much firmer footing."
Documentary evidence had suggested that epidemics, which raged through Europe in the late 15th and early 16th centuries, could be connected with the return of Columbus from America.
Skeletons found in the United States, which showed the disease present before 1492, seemed to support this theory.
Analysing bones
The skeleton was found in a churchyard in Rivenhall, near Chelmsford.
Tests on the Essex bones suggest the woman was aged somewhere between 25 and 50 years old.
The roughness of the bones and the pitted surface indicate she had syphilis.
Archaeologists from English Heritage believe this was the venereal form of the disease, caught through sexual intercourse.
Work including DNA tests will now continue on this and related specimens.
Dr Mays said he wants to find more evidence to convince doubters once and for all that syphilis was here before Columbus.
"Then the big question will be to find out exactly where this disease came from, if not from America," he added.