When did King Leopold II rule over the Congo?

The reign of King Leopold II ran from 1865, when he succeeded his father as King of the Belgians, to his death in 1909.  In between those dates was the ravaging of what was known as the Congo Free State, a large expanse of central Africa known after the king's death as the Belgian Congo, and, following independence, as Zaire and, today, following the ouster of Zaire's long-time and extremely corrupt ruler Mobutu Sese Seko, as the Democratic Republic of Congo.  A land rich in natural resources and possessing some of the world's most pristine jungle, it has known mostly hardship for more than 100 years.

King Leopold II was committed to expanding his personal overseas interests -- in effect, colonies -- and, after failing to buy the Philippines set his sights on the Congo.  To stake his claim, the king contracted with the explorer Henry Stanley to establish a colony there, and by 1885, the Congo was firmly entrenched as the king's possession, now called the Congo Free State.

For the people living in the Congo, it was all downhill from there.  The king ruthlessly exploited the region's resources, especially its rubber industry, and used the citizens as slaves to enrich himself.  Estimates of how many native Africans died as a direct result of King Leopold II's policies range into the millions.  A recent study of the period by Adam Hochschild titled "King Leopold's Ghosts," puts the number dead at 10 million.

King Leopold II's reign of terror in the Congo ended a year before his death as a result of mounting criticism of his brutal rule over that territory.  After relinquishing his hold on the Congo, the Belgian parliament renamed it the Belgian Congo, which it remained until achieving independence in 1960.

Who was King Leopold II and what was his relation to Congo?

The King Leopold II that you are referring to in this question was the King of Belgium.  He reigned from 1865 until his death in 1909.  He is connected to the Congo because he acquired that region as a personal holding (as opposed to a colony of the country of Belgium) and exploited it in a manner that was terribly brutal even for that time period.

In the late 1800s, a “scramble for Africa” occurred.  This was a time during which European countries were trying to take as much of Africa as they could for themselves.  At that time, people believed that countries needed to have empires in order to be strong and prosperous.  Countries like France and the United Kingdom already had empires and other countries were trying to catch up to them.

Leopold believed in the need for colonies.  Therefore, he tried to get various areas of the world for Belgium.  However, he did not do this openly.  Instead, he tried various ways to conceal what he was doing.  By the mid-1880s, he was able to get the international community to assign the Congo to a company that he owned.  It was disguised as a philanthropic organization.  The international community gave the company control and the company claimed that it was going to try to improve the lives of the natives.

Instead, Leopold caused horrible atrocities to be committed in the Congo.  He ran the colony in a brutal way, demanding that the natives work to make money for him (largely by producing rubber) and punishing them severely if they did not.  His regime was so brutal that the international community was horrified.  Pressure from the outside eventually forced Leopold to relinquish control of the Congo.  He was no longer allowed to rule it personally, but was required to give control of it to the Belgian government.

Thus, we can see that King Leopold II of Belgium was closely connected to the history of the Congo.