Imad Barghouti, 52, was arrested in April and imprisoned without trial for an initial three months, under an Israeli procedure known as administrative detention.
His lawyer said he was arrested for comments posted on his Facebook page.
He has been accused of inciting violence against Israel, and Israeli media have said he is suspected of ties to the group Hamas.
His lawyers appealed to an Israeli military court after his arrest, which in May ruled that he should be freed.
However military prosecutors opted to put him on trial, leading to his sentence on Sunday.
He was also given a fine of 2,000 shekels (450 euros, $525), according to the Palestinian Prisoners' Club. He could be released in a month if he is given credit for time served.
Barghouti is a professor at a university in the West Bank, occupied by Israel since 1967.
Israel's military did not immediately respond to a request for information.
Administrative detention allows Israel to hold prisoners deemed security risks without trial for periods of up to six months, renewable indefinitely.
About 7,000 Palestinians are in Israeli prisons, more than 10 percent of them in administrative detention.