Gyude Bryant was chosen on Thursday by fellow countrymen attending peace talks in Ghana.
He will lead the country's interim government from October, and his deputy will be Wesley Johnson, the chairman of the United People's Party.
The chairman's and the vice-chairman's posts correspond to the jobs of president and vice-president in previous Liberian administrations.
However, the functions have been renamed to stress the caretaker nature of the new government, aimed at bringing peace after four years of a brutal civil conflict.
Bryant, who is from the Liberia Action Party, was picked from a list of three candidates proposed by 18 political parties and other civil groups attending the Accra talks.
He is a leading member of the Episcopal Church in Liberia, but was considered to be the weakest of the three contenders for the top job.
The other two candidates were Ellen Johnson-Sirleaf, a veteran opposition figure, and Rudolph Sherman from the True Whig Party.
Former president Taylor was
forced out from power
Bryant said he was not taken aback by his nomination.
"I am not too surprised because the Liberians need a neutralist and I believe I am a neutralist," he said.
But a Liberian journalist said the decision took most people by surprise.
"Everybody said that Ellen (Johnson-Sirleaf) would be the right person at this time because of her connection with the United Nations and the international community.
"At this time when the UN is thinking of sending in a peacekeeping force under Chapter VII of the (UN) charter, it would been helpful to have someone like her," he said.
The new interim government is to remain in power until January 2006.
Elections are scheduled to be held in late 2005, according to a sweeping peace deal signed on Monday to end Liberia's war.