TEL AVIV—Prime Minister Benjamin Netanyahu of Israel was indicted on corruption charges, posing a heightened threat to his personal and political future and deepening uncertainty as the country hurtles toward an unprecedented third election in a year.

Attorney General Avichai Mandelblit said on Thursday that Mr. Netanyahu faces charges of bribery, fraud and breach of trust in connection with three corruption probes, marking the first time a sitting Israeli leader has been indicted.

Mr. Netanyahu’s political survival—and his legacy as Israel’s longest-serving leader—may now depend on whether the Knesset grants him immunity, which would pause the indictment until after he leaves that parliamentary body.

Mr. Netanyahu, who denies the charges and pledges to continue to lead the country, has so far retained the support of his Likud party and other right-wing political allies.

But Mr. Netanyahu’s grip on the Likud party, already threatened following his two failures to form a government since his last coalition collapsed nearly a year ago, is now more likely to be challenged in a third election.