Prince Shah Karim Al Hussaini Aga Khan (IV) (Persian: شاه کریم حسینی، آقاخان چهارم) (Aga Khan is also transliterated as Aqa Khan and Agha Khan), NPk, NI, KBE, CC, GCC, GCIH, GCM, born 13 December 1936, in Geneva, Switzerland; is a British business magnate, racehorse owner and breeder, as well as the 49th and current Imam of Nizari Ismailism – a denomination of Ismailism within Shia Islam consisting of approximately 15 million adherents (under 10% of the world's Shia Muslim population). He has held this position of Imam, under the title of Aga Khan IV, since 11 July 1957, when, at the age of 20, he succeeded his grandfather, Sir Sultan Muhammad Shah Aga Khan III. The Aga Khan claims to be a direct descendant of the Islamic Prophet Muhammad through Muhammad's cousin and son-in-law, Ali, considered the first Imam in Shia Islam, and Ali's wife Fatima az-Zahra, Muhammad’s daughter from his first marriage. As the Imam of Nizari Ismailism, the Aga Khan IV is considered by his followers to be the proof or hujjah of God on earth as well as infallible and immune from sin (just as an Imam is viewed in most other denominations of Shia Islam). He is further considered by his followers to be the carrier of the eternal Noor of Allah ("Light of God" – a concept unique to certain denominations of Shia Islam). In 1986 the Aga Khan ordained the current version of the Ismailia Constitution – an ecclesiastical decree affirming to Nizari Ismailis his "sole right to interpret the Qur'an and provide authoritative guidance on [all] matters of faith" and formalising his sole discretion, power and authority for the governance of Nizari Ismaili jamats (places of worship) and institutions.
Forbes describes the Aga Khan as one of the world's ten richest royals with an estimated net worth of US$800 million (2010). Additionally he is unique among the richest royals as he does not rule over a geographic territory. He owns hundreds of racehorses, valuable stud farms, an exclusive yacht club on Sardinia, a private island in the Mediterranean Sea, two Bombardier jets, a £100 million high speed yacht named after his prize racehorse, and several estates around the world, including an estate called Aiglemont in the town of Gouvieux, France, north of Paris. His philanthropic institutions, funded by his followers, spend more than $600 million per year – primarily in Africa, Asia, and the Middle East. In 2007 G. Pascal Zachary of the The New York Times wrote after an interview with the Aga Khan, "Part of the Aga Khan's personal wealth [used by him and his family], which his advisers say exceeds $1 billion [USD], comes from a dizzyingly complex system of tithes that some of the world's 15 million Ismaili Muslims pay him each year [one of which is called dasond, which is at least 12.5% of each Nizari Ismaili's gross annual income] – an amount that he will not disclose but which may reach hundreds of millions of dollars annually."
Among the goals the Aga Khan has said he works toward are the elimination of global poverty; the promotion and implementation of secular pluralism; the advancement of the status of women; and the honouring of Islamic art and architecture. He is the founder and chairman of the Aga Khan Development Network, one of the largest private development networks in the world. The organisation has said it works toward improvement of the environment, health, education, architecture, culture, microfinance, rural development, disaster reduction, the promotion of private-sector enterprise and the revitalisation of historic cities. Since his ascension to the Imamate of Nizari Ismailis in 1957, the Aga Khan has been involved in complex political and economic changes which have affected his Nizari Ismaili followers, including the independence of African countries from colonial rule, expulsion of Asians from Uganda, the independence of Central Asian countries such as Tajikistan from the former Soviet Union and the continuous turmoil in Afghanistan and Pakistan.