But his journey from a French foster home to a Brussels court began not in a Middle Eastern desert but in a run-down industrial town.
On Thursday, after a two-month trial in the Belgian capital, 12 jurors found the 33-year-old guilty of the four anti-Semitic murders during a shooting spree at Belgium's Jewish Museum on May 24, 2014.
He faces life in prison and is expected to be sentenced on Monday at the earliest.
Nemmouche, an athletic-looking man with a trimmed beard, told the court in his final testimony this week that he had been “tricked”.
He seemed to refer to arguments made by his lawyers that he was not to blame for the murders and had been caught up in some kind of plot targeting the Israeli intelligence agency Mossad.
Separately, he is also accused of acting as the jailer of four French journalists taken hostage by jihadists in Aleppo in 2013.
Nemmouche is already a case study in the radicalisation of some young European Muslims.
Belgium and France, in particular, fear the defeat of groups like the Islamic State in Syria will send more angry young men homewards.
But Nemmouche seems to have been on a radical path long before he set off, in early 2013, for the so-called “caliphate” on the Euphrates.
The investigation into the May 2014 massacre in the museum has pieced together elements of his background.
'Sadistic and narcissistic'