Recep Tayyip Erdogan and his Islamist-leaning Justice and Development (AK) Party have run Turkey since 2002.
Mr Erdogan came to office a popular politician. Charismatic and driven, he saw his support grow after his party helped bring economic and political stability to the country.
Mr Erdogan, pictured here with his wife, is a charismatic politician
But he has always had his secularist opponents, who accuse him and the party he founded of harbouring a secret agenda to turn Turkey into a religious society.
The prime minister's past is associated with hardline Islamic views, and his party has its roots in political Islam. But Mr Erdogan has sought to moderate his position since coming to government.
The country's generals - the guardians of Turkey's secularist constitution - however, have viewed this apparent moderation with suspicion.
Few critics, however, would deny that Mr Erdogan has presided over a government that has reformed and has modernised the country faster and more effectively than most of its predecessors.
The economy has grown strongly under his government. The constitution, the police, the army and the judicial system have all been reformed.
He also worked to improve relations with the US, which were strained after parliament voted against allowing US forces to pass through Turkey at the start of the Iraq war.
His reforms helped secure the start of Turkey's EU memberships talks, and led many Western leaders - George Bush and former British Prime Minister Tony Blair among them - to argue that Mr Erdogan's government can become a powerful example for Turkey's neighbours in Iran, Iraq and Syria.
Mr Erdogan has avoided the sensitive issue of Islamic dress for women, even though his own wife, Emine, wears a headscarf.
Because of Turkey's secular constitution, women are banned from entering government offices and schools wearing headscarves, to the annoyance of many religious-minded Turks.
But critics say his failed bid to criminalise adultery, and his attempts to introduce "alcohol-free zones" reveal his true intentions. He has also reduced the role of the military in the political arena
The issue of headscarves in Turkey is a sensitive one
Mr Erdogan's AKP party was formed by a breakaway group of the Virtue Party, which was closed by the courts in 2001 due to its "anti-secular" activities.
The prime minister has said he is committed to secularism, but he does not think it should be at the expense of Turks who want to express their religious beliefs more openly.
"The essential problem is to find a way to stay united, preserving our differences", he says. "Rights and freedoms are necessary for everybody."
In April 2007, Mr Erdogan became embroiled in a political crisis after he picked Abdullah Gul, the Turkish Foreign Minister, to be the country's next president.
Parliament, which chooses the president in a series of votes picked Mr Gul in the first ballot, but this was boycotted by the opposition who got the decision overturned in court.
Mr Erdogan has tried to settle crisis by calling for early elections.
The AKP won a landslide election victory in 2002. Its leader, Mr Erdogan, was unable to join his political colleagues in parliament because he was banned from holding political office.
But a speedy change in the law cleared the way for Mr Erdogan to run for parliament - and within days of his victory he had been named as prime minister.
Born in 1954, he is the son of a coastguard in the city of Rize on Turkey's Black Sea coast.
He was 13 when his father decided to move to Istanbul, hoping to give his five children a better upbringing.
As a teenager, he sold lemonade and sesame buns on the streets of Istanbul's rougher districts to earn extra cash.
He attended an Islamic school before obtaining a degree in management from Istanbul's Marmara University - and playing professional football.
Joining Islamist movement
While at university, he met Necmettin Erbakan - who went on to become the country's first Islamist prime minister - and entered Turkey's Islamist movement.
Mr Erdogan's first brush with the law came after the military coup of 1980, while he was working for Istanbul's transport authority.
Mr Erdogan's boss, a retired colonel, told him to shave off his moustache. Mr Erdogan refused and had to quit the job.
His political career in the Welfare Party, as the Islamists' party was known until it was banned in 1998, was developing fast.
In 1994, Mr Erdogan became the mayor of Istanbul.
Even his critics admit that he did a good job, making Istanbul cleaner and greener - although a decision to ban alcohol in city cafes did not please secularists.
He also won admiration from the many who felt he was not corrupt - unlike many other Turkish politicians.
His background and commitment to Islamic values appealed to most of the devout Muslim Turks who have been alienated by the state.
But his pro-Islamist sympathies earned him a conviction in 1998 for inciting religious hatred.
He had publicly read an Islamic poem including the lines: "The mosques are our barracks, the domes our helmets, the minarets our bayonets and the faithful our soldiers..."
He was sentenced to 10 months in jail, but was freed after four.