KUALA LUMPUR, Malaysia — Najib Razak, the former prime minister who sat at the pinnacle of a political machine that dominated Malaysia for more than 60 years, on Wednesday began to face the first of multiple corruption trials stemming from the disappearance of billions in public funds.

The allegations of graft at 1Malaysia Development Berhad, or 1MDB, the state-owned investment fund he founded, led to widespread public anger and to Mr. Najib’s electoral defeat last year. The upheaval reoriented Malaysian politics and left the former leader, who was once considered untouchable, facing the prospect of decades in prison.

“This is a sea change for Malaysian politics for the very simple reason that for the first time a former head of government has been charged with corruption,” said James Chin, director of Asia Institute Tasmania at the University of Tasmania.

Mr. Najib, 65, went on trial in Kuala Lumpur, the capital, as part of one of the biggest corruption cases in history to go to court. He faces dozens of charges over allegations of graft at 1MDB, which lost $4.5 billion that prosecutors in Malaysia and the United States say was funneled to his circle, including $731 million that went into his own bank accounts.