It is not explicitly stated who invented Parseltongue in the books. However, it's heavily implied that the ability originated from Salazar Slytherin, one of the four founders of Hogwarts School of Witchcraft and Wizardry.
Here's why:
* Salazar's connection to snakes: Slytherin was known for his affinity with snakes, which is reflected in his House's emblem.
* Parseltongue's connection to the Chamber of Secrets: The ability to speak Parseltongue is linked to the Chamber of Secrets, a hidden chamber built by Salazar Slytherin.
* Tom Riddle's ability: Lord Voldemort, who was a descendant of Salazar Slytherin, was a Parselmouth.
While the books don't explicitly state that Salazar created Parseltongue, the evidence points strongly towards him being the origin of the ability. It's possible it's an ancient magical language passed down through Slytherin's bloodline, with Salazar being a key figure in its history.