JERUSALEM — Ehud Olmert, the former prime minister of Israel who is serving a 27-month sentence for bribery, fraud, obstruction of justice and breach of trust, is expected to be released on Sunday after a parole board cut his sentence by a third.

The board’s decision on Thursday appeared to close a legal saga that has roiled Israeli society and politics for years. Mr. Olmert, forced to resign during an intensive, if inconclusive, round of peace talks with the Palestinians, was the first former head of government to be imprisoned for misconduct in Israel, though the crimes for which he was convicted did not take place during his tenure as prime minister, from 2006 to 2009.

Mr. Olmert entered prison in February 2016 after being convicted in various corruption cases. He acknowledged having made “mistakes” but has consistently denied criminal wrongdoing.

The parole board’s decision was a great relief to Mr. Olmert, 71, his lawyers said. Prosecutors, who opposed a commutation of the sentence, said later Thursday that they would not appeal the decision.