This diploma thesis explains the concept of oil, follows the development of the oil industry, and the changes in oil price from its beginnings. The author presents view of the global oil market structure, including the largest producers and consumers of oil. The annual and monthly reports of OPEC as the world's largest cartel, whose role in oil production (but also in oil price formation) is of great international importance were used in analyses. As the oil market is global, different types of oil exist, and with them their accompanying prices. Supply, demand, and geopolitics are the main factors which influence changes in oil price. This paper analyzes and describes these factors in detail, as well as other factors which can cause changes in oil price, thereby greatly affecting the world economy. The low price of oil, compared to self-renewable energy sources, makes oil the most used natural energy source. The market price of oil is expressed in dollars, so changes in the dollar exchange rate directly affect changes in oil price. This paper presents how the price of oil fluctuates when the dollar appreciates or depreciates.