What country has the largest oil reserves in the world?

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.