Said bin Zair, 57, a hard-line Islamist academic who was freed a year ago after eight years in prison for demanding reforms in the Saudi monarchy, was arrested again in April on charges of condoning suicide bombings in a television interview.
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According to the interior ministry, Zair was arrested over remarks on 15 April on Qatar-based Aljazeera television "in which he backed the terrorist acts in Riyadh which targeted Muslims and non-Muslims."
Zair was on a programme to discuss al-Qaeda leader Osama Bin Laden's offer to suspend attacks against European interests if they left Iraq.
Zair's son Abdullah said he would contest the sentence, announced without a lawyer, since "the judge said there was no need for a lawyer according to Sharia [Islamic law]."