The North Korea-flagged ship had been loaded at a rebel-held port and evaded a naval blockade before being boarded by US Navy Seals south of Cyprus.
Its evasion prompted parliament to sack Prime Minister Ali Zeidan.
The US said it had handed over the ship, cargo and crew to Libyan forces in international waters off the coast of Libya.
Rebels had loaded the Morning Glory with oil at the port of Sidra. It was unclear where it was heading.
It was the first vessel loaded at a rebel-held port since a separatist revolt against the central government in Tripoli erupted in July 2013.
Rebels under Ibrahim Jathran hold three ports, and are demanding a greater share of the country's oil revenue.
Earlier, the Lana state news agency reported clashes between his fighters and Libyan troops in his hometown of Ajdabiya.
The US embassy said in a statement that the handover of ship, cargo and crew had gone "smoothly and as planned".
It added: "We have been assured by the government of Libya that the captain, crew members and Libyan nationals who were aboard the stateless tanker will be treated humanely in accordance with internationally recognised standards of human rights."
The Navy Seals operation had been authorised by President Barack Obama and no-one was hurt.
The vessel was flagged in North Korea but officials in Pyongyang said it had been deregistered because of the incident. It was said to have been operated by an Egyptian company.
The Libyan government is still struggling to assert its authority on rebel groups that helped to overthrow Col Muammar Gaddafi.
The US says it has returned the rogue oil tanker Morning Glory to the Libyan government.