The outgoing US President had pledged to close the US military prison in Cuba before he left office, but his efforts have been hampered by Republican politicians.
Oman's foreign ministry did not release any details of the prisoners it has received, but said it had accepted the inmates at the United States' request.
Just days ago, authorities said 19 of the remaining 55 inmates at the camp had been cleared for release and could be freed in the final days of Mr Obama's presidency.
It is not the first time Oman, which is situated on the Arabian Peninsula, has agreed to receive inmates from the notorious facility.
It accepted 10 Guantanamo detainees from Yemen - which is in the grip of a civil war - in January 2016 and another six in June 2015.
Neighbouring Saudi Arabia took four prisoners from the camp earlier this month, while the United Arab Emirates took 15 prisoners last summer, to help bring the remaining population of the facility down.
However, Mr Obama's successor, President-elect Donald Trump, said during his election campaign that he wanted to keep the prison open and "load it up with some bad dudes".
The majority of Guantanamo inmates released have been sent to Pakistan, Saudi Arabia and Afghanistan.