Francois Fillon, who represents the moderate wing of the ruling Conservative party, is a close ally of Sarkozy and the driving force behind his election campaign.
Fillon's formal appointment to the premiership Thursday came as no surprise, with the 53-year-old MP tipped as the most likely candidate for the post ever since Sarkozy won the presidency in the May 6 runoff.
Fillon made his political mark while serving as social affairs minister between 2002 and 2004, and minister of education in 2004-2005.
The unpopular retirement and education reforms that he carried through in those years proved his ability to bring about transformations despite strong resistance to change - a quality seen as crucial to implementing Sarkozy's liberal reform agenda.
The president's plans to scrap the 35-hour working week and to set a minimum level of service during strikes by transport workers have already drawn criticism from trade unionists. And his declared intention to give more autonomy to universities has sparked massive student protests.
On the other hand, as the Figaro newspaper noted, Fillon is open to dialogue, which may prove an asset in working with the broad-based Cabinet envisaged by Sarkozy, one that would include centrists and leftists as well as Conservatives.
Analysts say that given Sarkozy's hands-on approach to social and economic issues - usually tended to by the prime minister and the Cabinet rather than the head of state - Fillon will probably not have much say in policymaking.
But then again, he does not seem overly ambitious, and may be quite happy with the role of "technical director," responsible for translating presidential decisions into reality.
In his 2006 book "France Can Stand the Truth," Fillon wrote that he favors "a French-style presidential regime," with the head of state managing the government.
Fillon joined Sarkozy's camp in 2005 after falling out with then-President Jacques Chirac, who did not offer him a new government post after the Dominique de Villepin Cabinet resigned over a rejection of the European draft Constitution in a national referendum.
Fillon then famously said: "Only my reforms will make Chirac's legacy memorable."
Media profiling Fillon note that he is a connoisseur of the legacy of 19th-century French writer and statesman Francois-Rene Chateaubriand. He reportedly goes in for soccer and mountain climbing, and is a passionate car racer.