Kurmanbek Bakiev won a landslide victory in elections in July
Mr Bakiev scored a landslide victory in the poll, winning 89% of the votes.
He had been appointed acting president in March, following the downfall of long-serving former leader Askar Akayev, who fled into exile.
Mr Bakiev, 55, who praised the conduct of the July elections, has said his main goal is to eradicate corruption.
He took the oath of office on the country's constitution in front of dignitaries in Bishkek's central square, following a military parade.
Mr Bakiev has said he will expect professionalism from members of his government, who he says will serve on the basis of merit rather than connections.
Analysts say Kyrgyzstan will have to develop industries such as tourism, hydro-electric power and mining if it is to create new jobs for its 5m citizens.
In his first post-election comments, Mr Bakiev questioned the need for the US to continue to have an airbase in Kyrgyzstan.
The Pentagon has since been told it can keep its base in Kyrgyzstan - but only for as long as it is needed for operations in Afghanistan. US-led forces have been stationed at the site near the capital, Bishkek, since 2001.
Ahead of the elections, Mr Bakiev's only significant political rival was thought to be Felix Kulov.
The two men agreed to a power-sharing pact, by which Mr Kulov would serve as prime minister if Mr Bakiev became president.
Kurmanbek Bakiev, July 2005
Kurmanbek Bakiev has been sworn in as the president of Kyrgyzstan after winning the elections one month ago with an 89% majority.

Following the exile of the previous president, Askar Akayev, Bakiev was appointed acting president until elections were held.

Mr Bakiev's main competitor in the elections was Felix Kulov. They agreed upon a power-sharing pact, meaning that Mr Kulov would become Prime Minister if Mr Bakiev became president.

Bakiev took his oath of office after a military parade, in front of diginitaries in Bishkek's central square.