Thomas Bach elected President of the IOC
The 59-year-old from Germany, a former Olympic fencing champion, won a comprehensive victory over five rivals in the vote in Buenos Aires.
Bach will succeed Jacques Rogge, who steps down after serving the maximum 12 years in the position.
In his victory address, Bach issued a call for harmony following an acrimonious election campaign which saw one of his rivals, Denis Oswald from Switzerland, reprimanded for his comments.
Bach told the IOC session: "Let us play together in harmony for a bright future under the leadership of the IOC.
"I would like to thank from the bottom of my heart all my friends and colleagues who voted for me - this is really an overwhelming sign of trust. I also thank my fellow candidates who I greatly respect.
"I will work with you in the coming years and repay your confidence. I know about the great responsibility of an IOC president."
Bach won in the second round of voting - the sign of an overwhelming victory - beating closest rival Richard Carrion, the Puerto Rican who is in charge of the IOC's finances, Ser Miang Ng from Singapore, Ukraine's Sergei Bubka, Oswald - the Swiss official who oversaw London's preparations for the 2012 Games - and C-K Wu, the Taiwanese head of the international boxing federation AIBA.
During the last few days Bach was forced to deny allegations in a German TV documentary about his conduct during his days as a fencer in the 1970s - it accused Bach of wearing a wet glove to fool the electronic scoring system - plus other claims about his business activities. A spokesman for Bach said the claims were "nonsense".
The figure in the background of this election is the man regarded as the IOC's 'fixer', Sheikh Ahmad al-Fahad al-Sabah, a member of the Kuwaiti royal family.
Al-Sabah is head of the Association of National Olympic Committees (ANOC), the umbrella group of 205 national Olympic committees which enjoys huge influence, not least through administering the Olympic Solidarity fund which has 438million dollars (£300million) to distribute between now and 2016 to needy projects.
That led to a backlash by Oswald who is concerned he is wielding too much power. Oswald told Swiss broadcaster RTF: "The members must make their decision but some don't like the link between Bach and Kuwait.
"I want an independent candidate who is not dependent on certain alliances."
Bach won by a landslide in the second round of voting, with 49 votes compared to 29 for nearest rival Carrion.
Ng attracted six votes, Oswald five and Bubka four after Wu had been eliminated in the first round.