Suure-Jaani is a town in the northern part of the county of Viljandimaa in Southern Central Estonia, 25 kilometres north of the town of Viljandi. Suure-Jaani is the centre of Suure-Jaani rural municipality. The oldest archaeological findings from the area date back to the 6th millennium B.C. At the end of the 12th century A.D., the Lehola hill fort of ancient Estonians was built at a location (now known as Lõhavere) approximately two kilometres north-east of the present town border. The hill fort was the centre of the northernmost district (Estonian: kihelkond) in the historical Estonian county of Sakala and also one of the centres of Estonians' fight against the conquest of German Sword Brethren in the 13th century. Not much except the hill remains of it but the place (known in Estonian also as Lembitu linnamägi) is still visited as a tourist attraction. 2/3 of the hill-fort have been excavated archaeologically.
During the following centuries, Suure-Jaani was one of the centres of Suure-Jaani parish and, since the end of the 19th century, also the cultural and commercial centre of the parish region.