From ancient India the game spread to Persia (present day Iran). Tradition has it that a Hindu ambassador brought a chess set to the ruler of Persia in the 6th century. With the rise of Islam, the game was spread to the Arabs, who in turn spread the game to Byzantium.
Whenever a culture discovered the game, the game changed. An example of this was the re-naming of the pieces. In India, the most important piece was called the Rajah, in Persia it was called the Shah, in the Arab world it was called the Caliph, and in Europe it was called the King. Although many other pieces were added or removed from the game over time, the most important piece has always been the ruling piece, whether it has been called Rajah, Shah, Caliph or King.
It was also spread by traders traveling the ancient trade routes from India. This resulted in variants of the game that still exist in China, Korea, Japan, India and other countries. The game variant that is most well known in the western world came from Persia to the main trade routes of Spain and Italy around 1000 AD. The game that we know today spread all over Europe, and by 1400 AD was well established and being played under most of the rules that still apply to the game today.
The first international tournament was held in London in 1851. This first tournament was not officially sanctioned, so the winner of it, a German named Adolf Anderssen, was known unofficially as the world's best player. It was not until 1866 that the first official international chess tournament was held, also in London. Wilhelm Steinitz from Bohemia won this tournament, and was the first official World Champion.