Prime Minister Mohamed Abdullahi Mohamed replaces Omar Abdirashid Ali Sharmarke, who had a long-running feud with the president and resigned last month.
A statement from the Somali government said that Mohamed is a former Somali diplomat, though it did not provide further details. The statement said Mohamed is an "educator who specialises in leadership skills, project management and conflict resolution."
Mohamed has a master's degree in political science, it said. Mohamed will be asked to name a Cabinet within one month. Mark Bowden, a top UN official with oversight of Somalia, said Mohamed's Cabinet is expected to be smaller than the bloated group of politicians that Sharmarke had control over.
Among officials in Sharmarke's Cabinet was a minister of tourism in a violence-plagued country that sees only a handful of tourists each year.
Somalia's Transitional Federal Government controls only a few blocks of Mogadishu and is generally seen as corrupt, weak and ineffective. The government has accomplished little since its inception in 2004.
Somalia hasn't had a fully functioning government since 1991, when warlords overthrew the president. The US last month announced a new, dual track approach to Somalia that will see continued American support of the transitional government but also new, direct support of other groups and regions in Somalia.
The new approach includes increased support to the semiautonomous Somali regions of Somaliland and Puntland.