Sheikh Ahmed Moaz al-Khatib was elected president of the National Coalition for Syrian Revolutionary and Opposition Forces, shortly after the new alliance was formed at a meeting in Qatar on 11 November 2012.
He resigned from the post just four months later, saying he wanted a freedom to work which an official institution could not allow him.
Mr Khatib is a former imam of the Umayyad Mosque in Damascus and a respected figure within Syria.
He was imprisoned several times for his criticism of the government during the uprising against President Bashar al-Assad before he fled the country and settled in Cairo.
Mr Khatib is not allied to any political party and is known as a moderate who has called for political pluralism and strongly opposes sectarian divisions among Syrians
"We demand freedom for every Sunni, Alawite, Ismaili (Shia), Christian, Druze, Assyrian ... and rights for all parts of the harmonious Syrian people," he said after being elected leader of the National Coalition.
Born in 1960, Mr Khatib comes from a well-known Sunni Muslim Damascene family. His father, Sheikh Mohammed Abu al-Faraj al-Khatib, was a prominent Islamic scholar and preacher.
Mr Khatib originally studied Applied Geophysics at university and worked for six years as a geologist at the al-Furat Petroleum Company.
He later rose to prominence as an Islamic preacher, becoming the imam of the historic Umayyad Mosque in Damascus about 20 years ago, following in the footsteps of his father.
After he was banned from preaching during the rule of Mr Assad's father, the late Hafez al-Assad, Mr Khatib began to operate underground.
According to the Reuters news agency, he taught at the Dutch Institute in Damascus and campaigned for democratic reform as part of the Damascus Declaration, a coalition of political parties, human rights groups and pro-democracy activists named after a document signed in 2005.
Mr Khatib also established the Islamic Civilisation Society, and taught Sharia (Islamic Law) at the Sheikh Badr al-Din al-Husni Institute in Damascus, and Daawa (Call to Islam) at the Tahzib Institute for Sharia Sciences.
His expertise saw him travel to many other countries to teach, including Bosnia-Hercegovina, the Netherlands, Nigeria, Turkey, the UK and US.
Mr Khatib also set up an Islamic website, Darbuna.com, which says its aim is "communicating with fellow preachers and conferring with them about the best way to call to God and preach about him".
A biography of Mr Khatib, circulated by opposition member Mulham al-Jundi, said he was known in Syria for advocating social justice and a multi-party political system, and for rejecting sectarianism.
In April 2012, a month after anti-government protests erupted in Syria, he gave a speech to a crowd in the Damascus suburb of Douma mourning Sunni demonstrators who had been shot dead by security forces.
"We are raising our voice for freedom for every human being in this country," he was quoted as saying by Reuters.
His support of a peaceful uprising resulted in him being arrested four times by the security forces, most recently at the end of April 2012.
He is currently said to suffer from back problems caused by a car bomb explosion that hit the security compound where he was being held during his last period of detention.
Mr Khatib fled to Cairo in July, reportedly after friends warned him that he risked being killed by the security services or "disappeared".
The Syrian writer and broadcaster Rana Kabbani told the Guardian that Mr Khatib was a "unifying figure and not a divisive one".
"He is not what he seems. He is not a traditional Islamist. He is not the traditional Sunni. He is someone who has all of Syria at heart."
Mazen Adi, a human rights defender and politician who once worked with Mr Khatib, said he could "play a role in containing extremist groups".
Soon after arriving in Cairo, Mr Khatib told Reuters that the president's Alawite minority sect had been treated unjustly "because the state used them and put them at the forefront" of the conflict.
And in a speech last month published on Darbuna.com, he was critical of the role Islamist militants had played as the violence has escalated, saying their prominence had allowed Western countries to portray the uprising as "extremist".
But Mr Khatib also insisted that the revolution remained peaceful.
"The arrogant regime left Syrian people with no choice but to take up arms as Syrians were compelled to do so in order to defend their religion, families and properties."
Shortly before he was elected head of the National Coalition, Mr Khatib circulated an open letter in which he argued that the actions of rebel fighters, some of whom have been accused of atrocities, should not be equated with those of the security forces under President Assad and his father.
"We are required to act peacefully and justly. But... we cannot employ Platonic idealism to judge those who risk their lives against a barbaric campaign," he warned.