There is no definitive answer. For the most part, hotels and other tourist-oriented facilities have the US-style 2-prong outlets with one side wider than the other. My $.99 adapter has worked in every hotel I've visited - until last week in a small place in the outback of Hokkaido. The plug just wouldn't go into the wall outlet. Luckily, I still had an old Japanese adapter I picked up years ago squirreled away in the bottom of my laptop case and it fit fine. I'd say in most hotels you are liable to use, the answer is yes. If not, ask the concierge for directions to the nearest Yodobashi or other electronics store and buy one. The hotel may actually have them. Or, you can go to Radio Shack or similar and buy an adapter specifically made for travel.