French law requires that you always have personal ID about
your person, so keep your passport on you to avoid trouble with the
EU nationals entering France need only a national identity
card; visitors from the UK should take their passport. In any case, airlines
usually ask for passports.
Nationals from other countries must be in possession of a
valid national passport.
There is no requirement for a visa for EU nationals, nor for
citizens from the US, Canada or Australia travelling as tourists and staying
for less than 90 days, except for students planning to study in France.