A precocious and brilliant student, Stengers entered the Free University of Brussels in 1939, at the age of 17.
He published his first scholarly article two years later in the Revue belge de philologie et d'histoire (Belgian review of philology and history).
In 1948, he presented his doctoral thesis under the direction of Professor Bonenfant on the historical bases of the national sentiments of Belgium.
"From this time," said the historian Ginette Kurgan, "the astonishing eclecticism of his interests is manifest, reinforced by a rigour of approach stimulated by his training as a medievalist."
Stengers' doctoral students included Jacques Brassinne de La Buissière and Louis-François Vanderstraeten [fr].