His appointment was seen as a strategic move by 39-year- old Macron, a former minister in the outgoing Socialist government who is trying to woo modernisers of all stripes to his new centrist party, La Republique en Marche (Republic on the Move, REM).
France's youngest ever president has already attracted dozens of Socialist MPs to his side, triggering a major realignment in French politics that has left the traditional parties floundering.
Like Macron, Philippe is a product of France's elite ENA college for senior public servants and worked for a while in the private sector.
Relatively unknown outside his Le Havre fiefdom, he has already crossed the floor once in his career, defecting from the Socialists to the Republicans as a young politician.
One of Macron's aides welcomed his appointment as "a good move", telling AFP it would help him "break the right".
Taking office yesterday, the former investment banker who trounced far-right leader Marine Le Pen in the May 7 presidential run-off, said he aimed to restore France's shattered self-confidence.
The fervently pro-European Macron also said he would help rebuild the flagging European Union.
He heads to Berlin later today for talks with German Chancellor Angela Merkel on how Europe's power couple can drive reforms of the bloc.
Like Macron, France's new prime minister has little truck with the entrenched left-right divide.
After campaigning for Socialist prime minister Michel Rocard as a youth, he switched to the right, becoming a close ally of centre-right former prime minister Alain Juppe.
Mayor of Le Havre, his home town, since 2010, the German-speaking father of three, who writes crime novels in his spare time, was elected to parliament in 2012.
His first task will be to help Macron finalise his cabinet choices, to be announced on Tuesday.
France's new president has said he wants a mix of experience and new blood -- a balance he has attempted to achieve in his slate of candidates for the June 11-18 election.