What is the charge on a #"surfactant"#?
Surfactants are usually the alkali metal salt of a long chain fatty acid. So the answer is
To a first approximation a surfactant, a detergent, is the salt of a carboxylic, or sulfonic acid, with a long alkyl chain attached. The counterion is usually a simple metal cation, i.e.
There are (I think!) both also cationic, for instance long chain long-chain alkyl ammonium salts, and neutral (i.e. amphiphilic) surfactants available, but these are a bit less common.