Minimum passport validity for travelling to Japan
I'm planning to travel to Japan and I just realised my passport will have less than six months validity at the time I travel.
I know some countries require at least 6 months validity for entry. Is this likely to be a problem for Japan?
(As an Australian citizen I don't require a visa for short term tourist entry)
It can often be hard to find out in advance for some countries whether they require six months validity or not, so the safest option is always ensuring your passport is renewed well before that six month period.
Fortunately though, for Japan, there's a fairly authoritative answer on this:
Some Asian countries require 6 months passport validity for me to enter. Does it apply to Japan? The passport must remain valid during the period of the stay but there is no minimum period of validity required.
(from the FAQ page of the Consulate-General of Japan, Melbourne)
Note that this applies to entry, not neccessarily to a visa application (as noted by @TheWanderingCoder in the comments). If you do require a visa, it is likely that a six month validity will still apply to this (eg. Pre-College Student Visa, College Student Visa, Working Holiday Visa, Working Visa, etc).
It may be of note that this seems to ONLY apply for the short term tourist Visa. As an Australian living in Japan (and who has had many different types of visas) almost all other visas require 6 months validity (Pre-College Student Visa, College Student Visa, Working Holiday Visa, Working Visa). Also note that both the Perth and Melbourne Consulate General websites information for other visas is now (especially in the case of Melbourne) woefully out of date (however the information for the short-term Visa is still current).