This may seem like an odd question but someone had to have invented it. I’ve looked everywhere but can’t find it. Thanks in advance. 
Do you mean a luffa? They are actually akin to sponges and the original ones were once living organisms, the ones you see these days are mostly synthetic, of course (just like you don’t see many real sponges in houses anymore.) The difference I believe between a real luffa and a real sponge is I believe a sponge is an animal and luffas were plants when alive. Just like sponges they have been used for pretty much ever by peoples who live by the oceans/seas.
The OP means these, made of nylon net. They’ve been around for about a decade as far as I know (UK).
I daresay prehistoric man used a bath pouf made from plants, and so on until fabric was invented, and then through the ages. Do you mean who actually invented it out of nylon net, like patented it? No one! It’s like asking who invented the towel. Maximus Towelus, Rome, 128 B.C. when he tore up an old worn out toga to dry his glutteus maximus.
For as long as I’ve been reading the newspaper, Heloise (the original one) had a household hints column, and she was constantly promoting “nylon net” scrubbers for household cleaning. I don’t remember if she advocated them for cleaning human bodies as well, but I’ve been reading the newspaper on a daily basis for about 48 years now.
Springtime is right, that’s what I was looking for. Well, surely someone had the idea. However, I had no idea they’ve been around for a decade. They may have been but I never noticed them until recently, as in a few years back. Though even so it’s just a curiosity thing really.
Right, I’m totally aware of those–the general tool itself has been around for thousands of years. Greeks and other peoples who lived by the ocean have used sponges and the husks of certain plants to clean themselves, as all purpose household sponges, as padding in armor and etc for as long as those peoples have had a history.
Since natural sponges and luffas must be harvested in an expensive process, I would say that some nameless researcher at a major chemical company was the head on a project team that very early on created these out of modern materials.
It’s like asking who invented plastic flatware, you might be able to find out, but the reality is the moment modern cheap materials became available people working for major chemical and manufacturing companies quickly recreated virtually every common household item in a newer, cheaper form that they could sell for a quick profit.
As far as I am aware, the loofah (local spelling in Zimbabwe) was “invented” by evolution - it is the dried interior structure of the cucumber-like fruit of a vine found in various parts of the world (members of “Luffa” genus)
It is very common to see Zimbabweans walking the streets selling loofahs and loofahs on sticks (for back scratching)
As to who first used a loofah for washing himself, that is lost in history. But I like to think he was Zimbabwean.