Mr Philippe could also attract other Republicans to Mr Macron's cause as the centrist president works to piece together a majority in parliament to pass his promised economic reforms.
Mr Macron's trip to Berlin, his first as president, signals his intent to also move rapidly on campaign promises to revive support for the European Union by reforming and strengthening it.
It is the first time in modern French political history that a president has appointed a prime minister from outside his camp without being forced to by a defeat in parliamentary elections.
Mr Philippe began his political life as a Socialist activist, before switching sides and serving as Mr Juppe's campaign spokesman during the Republicans party primary.
He said: "This is an individual decision".
By appointing Philippe, Macron has passed over some loyal followers including Richard Ferrand, a former Socialist who was one of the first to join Macron's cause a year ago and is secretary general of REM.
By appointing him, Macron has passed over some loyal followers including Richard Ferrand, a former Socialist who was one of the first to join Macron's cause past year and is secretary general of REM.
Elysee secretary-general Alexis Kohler made the announcement on the steps of the presidential Elysee palace.
The remainder of Mr Macron's government is expected to be announced on Tuesday.
Philippe is a close associate of former prime minister Alain Juppe, who leads the moderate wing of The Republicans and has indicated that he favours helping Macron.
The head of France's main rightwing party reacted coolly on Monday towards the appointment of conservative Edouard Philippe as prime minister, saying it was an amibiguous move and unclear what political line he would follow.
Juppe said he would be backing LR lawmakers in the mid-June elections, and not Macron's candidates.
When Mr Juppe was beaten, the 46-year-old pledged his support to Francois Fillon but later quit the campaign when prosecutors started investigating allegations that the presidential candidate gave family members taxpayer-funded "fake jobs".
Mr Philippe is the mayor of the Normandy port of Le Havre, a trained lawyer and an author of political thrillers.
Mr Philippe's appointment ticks several boxes for 39-year-old Mr Macron, France's youngest president, who took power on Sunday.