Can I sleep in the Fukuoka Airport overnight?

I will have a Monday 7:20 am flight up to Tokyo (and then onto US) and instead of leaving from around Sasebo early in the morning, was just going to get a bus on Sunday evening, get into the airport and camp out. Is that allowed, does anyone know? Thank you!

No.

https://www.fukuoka-airport.com

the airport is surrounded by residential areas and the airport only operates from 7 am to 10 pm.

https://www.sleepinginairports.net/asia/fukuoka.htm

Overnight stays are not permitted at this airport.
For uninterrupted sleep, there are hotels near the airport.

The airport is really close to town anyway, about 10 - 15 minutes - so you should be able to get in quickly

Thanks for the quick reply and useful information; that helps me knowing what to plan for, ahead of time.

As already answered, no.

But there are many cheap places to stay - there are 3 Toyoko Inn hotels near Hakata Station, plus 1 Superhotel.
https://www.toyoko-inn.com/hotel_list/
http://www.superhoteljapan.com/en/
and next to the Nakasu-Kawabata subway station, there is a First Cabin.
https://first-cabin.jp/en/hotels/19
....to name a few.

If you have time, you really should see the city. It has some wonderful sights, and many unknown to most.
http://www.thejapanfaq.com/fukpic.html