Judges at the Semarang District Court said Pujiono Cahyo Widianto, 46, was found guilty of sexually abusing a minor.
The cleric, who also ran an Islamic boarding school and owned several businesses, hosted a lavish wedding in Central Java province in 2008 that was attended by thousands of people.
He claimed at the time he hadn't done anything wrong because he had no plans to consummate the marriage until the girl reached puberty.
But few in the predominantly Muslim nation of 237 million were mollified, especially when he went on to say he also intended to marry two other girls, aged 7 and 9.
Muslim men can have up to four wives in Indonesia but they must be older than 18.
Complaints came from the religious affairs minister, child rights groups and the Indonesia Ulemma Council - the country's top Islamic body.
In addition to sentencing Widianto to prison, presiding Judge Hari Mulyanto ordered him to pay a 60 million rupiah ($6,690) fine.
Widianto, who said he would appeal, has been in detention since early last year.
Police returned his young wife to her parents soon after the wedding.