He reigned from 1328 until his death.
Philip's reign was dominated by the consequences of a succession dispute.
When King Charles IV died without a male heir in 1328, the nearest male relative was his maternal nephew Edward III of England.
It was held in France, however, that Edward was ineligible to inherit the French throne through the female line according to the ancient Salic Law.
Philip, being Charles IV's cousin in the male line, acceded instead.
At first, Edward seemed to accept the Valois succession to the crown, but he pressed his claim to the throne of France after a series of disagreements with Philip.
The result was the beginning of the Hundred Years' War in 1337.
After initial successes at sea, Philip's navy was annihilated at the Battle of Sluys in 1340, ensuring that the war would occur on the continent.