Sometimes a very simple question does not result in a simple answer. I could say the country is either Saudi Arabia or Venezuela, depending on whose numbers you trust the most.
It is cited in many references that Saudi Arabia has the highest proved reserves, totalling 267 billion barrels. See links.
However recently, Venezuela claims to have the most proven reserves, with 297 billion barrels. See second link and last link.
Note that million and billion barrels is abbreviated MMbbls and Gbbls.
Both Saudi Arabia and Venezuela have extensive oil deposits and for many years, Saudi Arabia claimed the most oil, with Venezuela more than 100 billion barrels less than Saudi Arabia. As shown on the related link, Venezuela has been raising its estimate of reserves for the past 5 years, and some of this oil may not be as "proven" as in the case of Saudi Arabia.
To meet the proven category, it is necessary to show the oil can be commercially developed under existing technologies and oil prices. Also, the oil recovery factor should be conservatively estimated.
Venezuela has extensive heavy oil deposits, and estimation of a conservative recovery factor may be subjective, allowing for overestimation of recovery. Their rapid increase in reserves has added skepticism of their claim to have the largest proven reserves in the world. Note the official OPEC estimate of reserves, in 2008 was 99.4 billion barrels. (see first link)
Saudi Arabia has not revised their estimates in many years, and according to Wikipedia, some experts suspect that their estimate may also be overestimated.
Venezuela has the largest oil reserves in Latin America.
The largest oil reserves in the world are located in Saudi Arabia. The country holds approximately 16% of the world's proven oil reserves.
Venezuela has the largest oil reserves in the world, with significant deposits located in the Orinoco Belt.
Algeria is the North African country with the largest supply of oil reserves.
USA
Venezuela has the largest oil reserves in Latin America.
The largest oil reserves in the world are located in Saudi Arabia. The country holds approximately 16% of the world's proven oil reserves.
Venezuela has the largest oil reserves in the world, with significant deposits located in the Orinoco Belt.
Algeria is the North African country with the largest supply of oil reserves.
Algeria famous because it is the tenth largest country in the world, the 17th largest oil reserves in the world and the 9th largest reserves of natural gas.
USA
Algeria is the tenth largest country in the world and the largest in Africa and the Arab world. Algeria has the 17th largest oil reserves in the world and the second largest in Africa while it has the 9th largest reserves of natural gas.
Saudi Arabia has the largest oil reserves in the world.
Saudi Arabia has the most oil reserves in southwest Asia, making it one of the world's largest oil producers.
Libya has the largest supply of oil reserves in North Africa. It is estimated to hold the largest proven oil reserves in Africa.
Saudi Arabia has the largest oil reserves in the region.
Venezuela has the largest crude oil deposits in the world, with the largest reserves located in the Orinoco Belt.