Who sets oil prices officially?.. Is there a firm or a body?

Answer 1

Organization of the Petroleum Exporting Countries (OPEC) now having 11 member countries, sets the oil price for international market.
The members of OPEC negotiate on matters of petroleum production, prices and future concession rights. The members agree on the quantity and price of oil exported.
OPEC was founded in Sept. 14, 1960 in a conference in Baghdad, with its 5 member countries namely Iran, Iraq, Kuwait, Saudi Arabia and Venezuela. Now the total members stand at 11. The rest 6 members are Indonesia, Qatar, United Arab Emirates, Algeria, Libya and Nigeria. Its head quarter is situated in Vienna, Austria.
The member countries of OPEC hold about 70% of world's oil reserves and supply about 40% of the world's oil.
There are other oil producing countries. They are Norway, Russia, Canada, Mexico, USA, Oman and Yemen. But they are not the member of OPEC.

Answer 2

Yes. The OPEC or Oil Producing Exporting Countries sets oil prices for their oil, and the rest of the countries matches it.