The 40-year-old father of two children brings to the job a burning passion to dump the austerity policies that his party says have brought a "humanitarian crisis" to Greece, and he knows he has little time to lose.
"It would be good to speed up the procedure because we have an uphill road ahead," he told President Karolos Papoulias as he received his mandate to form a government.
On his first day as prime minister, Tsipras showed he is big on symbolism.
Tsipras also became the first Greek prime minister to take a civil rather than religious oath of office, and to dispense with a tie at the ceremony.
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In his victory speech yesterday, he pledged to end the "humiliation" and "vicious circle" of austerity for the good of Greece and other European nations.
The young leader will govern in a coalition with the nationalist Independent Greeks party after securing 149 seats in yesterday's election, two short of the required majority in the 300-seat parliament.
The Greek public first learned his name in 1990 when as a 17-year-old he led a school sit-in and told a TV interviewer: "We want the right to judge for ourselves whether to skip class."
An engineer by training, Tsipras was born in an Athens suburb in July 1974, a fateful year for Greece. It marked the collapse of a seven-year army dictatorship that mercilessly persecuted leftists and Communists, and culminated in a bloody crackdown against a student uprising.