More specifically, the first battery-operated sex toy was a voltaic pile, which was the primitive form of the battery. Unfortunately, this particular voltaic pile was made by Johann Ritter, who put it to unnatural, but entertaining, uses.
Johann Ritter was a brilliant young scientists with many major accomplishments. His most famous scientific contribution was the discovery of ultraviolet light. Less well-known is his invention of the first battery-operated sex toy. It was very stripped down. It was, in fact, just a voltaic pile and some wires.