Hard to say which CULTURE is likely to shower the least for cultural reasons. Europeans, of course, shower less often than Americans and don't really seem that much the worse for it. We have smelly Americans just as they have smelly Europeans, both in the minority, thank goodness.

But my mind immediately went to the parts of the world where not culture, but rather weather and geography determine how often bathing by any means is possible. Desert cultures would, obviously, bathe with water very seldom, keeping clean mostly by other means (sand "baths," etc). And of course any part of the world afflicted by drought would find its cultural norms for bathing radically shifted by scarcity.

Until recently, Americans seldom, if ever, had to worry much about actual shortages of water. Most of us have plenty and don't pay that much for it. So it's no wonder we bathe and do laundry quite a bit more often than most of the world.

Did you have a guess based on personal experience?

Just throwing it out there, but most likely various African cultures, not because they don't want to but probably because they only have access to less then 2 gallons of water a day.

http://www.youtube.com/watch?v=HW5eBfZhE4M

The Funny Answer the French...
The real answer can be split in to two categories the modern world and the undeveloped world. In the modern world the least number of showers per week title in my opinion would go to lower class citizens of countries like India, and Mexico. The reason not being that these people don't bathe but due to the fact that the more common way of getting clean is a bath in a bathing pool, lake, or stream. As for the undeveloped portion of the world the reasoning would be the same, as the more common way of getting clean is a bath in a bathing pool, lake, or stream. This would be tribal group around the world in places such as South America and Indonesia.