NEW ORLEANS — A day of reckoning arrived for BP on Thursday as the oil giant agreed to plead guilty to a raft of criminal charges and pay a record $4.5 billion in a settlement with the government over the deadly 2010 disaster in the Gulf of Mexico. Three BP employees were also charged, two of them with manslaughter.

The settlement and the indictments came two and a half years after the fiery drilling-rig explosion that killed 11 workers and set off the biggest offshore oil spill in U.S. history.

The settlement includes nearly $1.3 billion in fines, the largest criminal penalty in the nation’s history. As part of the deal, BP will plead guilty to charges involving the 11 deaths and lying to Congress about how much oil was spewing from the blown-out well.

“We believe this resolution is in the best interest of BP and its shareholders,” BP chairman Carl-Henric Svanberg said. “It removes two significant legal risks and allows us to vigorously defend the company against the remaining civil claims.”

Assistant Attorney General Lanny Breuer said the deaths and the oil spill “resulted from BP’s culture of privileging profit over prudence.”

Separately, BP rig workers Robert Kaluza and Donald Vidrine were indicted on federal charges of manslaughter and involuntary manslaughter, accused of repeatedly disregarding abnormal high-pressure readings that should have been glaring indications of trouble just before the blowout.

In addition, David Rainey, BP’s former vice president of exploration for the Gulf of Mexico, was charged with obstruction of Congress and making false statements. Prosecutors said he withheld information that more oil was gushing from the well than he let on.

Rainey’s lawyers said he did “absolutely nothing wrong.” And attorneys for the two rig workers accused the Justice Department of making scapegoats out of them. Both men are still with BP.

“Bob was not an executive or high-level BP official. He was a dedicated rig worker who mourns his fallen co-workers every day,” Kaluza attorneys Shaun Clarke and David Gerger said in a statement. “No one should take any satisfaction in this indictment of an innocent man. This is not justice.”