Can I travel to Japan with a newborn

Trip will be 5-6 days but I can't find any info on rules of infant travel. Baby will be around 8 weeks.

I don't see any reason why you can't, the baby would need his/her own passport.

In addition to a passport, if you are traveling alone with the baby, you might require a letter signed by both parents. I don't know the exact details of what this letter contains.

You can fly to Japan with an infant. But as noted, the child must have a passport. If you are a US citizen, with the current backlogs and delays, it is doubtful you will be able to get the infant's passport within 8 weeks of birth. You will need to expedite it (extra fees) to have any chance of getting it on time.
As also noted by others, if you are travelling without the childs father, you should carry a notarized letter from him acknowledging & authorizing you to take the infant out of your home country. I know of at least one person who was not allowed to travel without such permission. Carry the signed one & at least one copy.
Also, make sure to contact the airline early, since you will need an infant ticket (most no longer allow infants, even when held by a parent, to fly for free). You may also be able to book a bulkhead seat and get a crib which attached to the bulkhead. Make sure to ask the airline about this and get clear written documentation on who arranges for it/who makes sure it is on the plane. My wife flew with American Airlines last year with our infant and the crib turned out to be a pain, check-in said the gate crew was responsible, gate crew said the check-in or flight crew was, etc... Major hassle.
Good luck!

Unless there is some urgent reason for you to come to Japan please for the sake of everybody else on the plane don't do this! Maybe if it's a short flight it would be ok but if your thinking about long distance from the States wait a few years. I have made the trip back and forth many times. Most of those trips blend into each other but 2 stand out. They were both planes that contained infants that SCREAMED the entire 13 hours. The mothers were doing everything they could including apologizing to other passengers the whole plane was hating these women. Just aweful.

Heidi, I'm not sure how far you are traveling from, but a 6 days trip sounds pretty busy for someone traveling as far as from the U.S. mainland, Australia or Europe. Maybe Korea would be near enough to Japan.

Either way, it is not really customary for Japanese locals to do a lot of traveling with an 8 week old. Perhaps one would do a quick homecoming flight and take it very slow once they are at their destination, meaning no sightseeing or dining out.

So I can't really tell whether touring Japan will be convenient for you or not. Not many people have done this; touring while constantly breast-feeding, loosing sleep, not being able to use a light-weight stroller, being away from your home doctor, etc. AND being in a different climate and time lag. Also infants change dramatically in a few days, and things can be very unpredictable.

Just thought you'd like to know. It's up to you.

Any chance that you could leave the baby at home with a relative if you must travel to Japan for 1 week only? my brother and I lived with older relatives for a couple of months at a time when we were very very young. Our country was at war and my parents, by no choice of their own, were in a very unsafe situation. It didn't harm us(I don't remember my first 3 years, only the sirens and the bombings on year 4).

Leaving an 8 week old with someone else? Hmm, that sounds even harder to me, and not worth it if it's leisure. It's not a 12 months old, you know. Again, it's up to the mother.

I should clarify that my wife and kids were going home to visit Okaasan & Otoosan for 2 months when they flew over, the baby was 3 months old. We got the passport 2 week before they left and we applied 1 week after she was born. We were sweating it.
When my wife got to Japan, she had Okaasan and her sister for support, babysit, provide strollers & carseats, etc.. I can't imagine making the trip without any support base when you got to Japan.

The baby did well on the way over, slept almost the whole trip except to feed. But the trip back she did not do as well and she cried a lot. Not the whole trip, but enough to make her voice heard!. My wife had to hold her most of the way and got little sleep herself.

I really can't imagine why a mother with a 8 week old baby is going to Japan for a holiday?? I mean, my sister recently gave birth to a lovely baby-girl, and she's all day busy with the little girl, so I can't imagine this?? or are you gonna visit relatives in Japan or so??

Not that I have anything to add to this thread, but I can imagine a lot of reasons for someone to have to travel with a newborn...but eight weeks old is way less trouble than an older baby. Flight could be difficult but the rest, well, coping with a baby is coping with a baby. Be comfortable with whatever means you have of carrying the baby - I don't recommend a stroller on the trains, it's done, and I see a lot of them, but if you can take little eight-weeker around on your person, it would be easier.

Just wanted to thank everyone who responded to my question. Of course the trip would not be "for Holiday" But the filing for passport might be my excuse for staying in the states. You need a birth cert. and baby might not have hers in yet.