Who is credited with inventing tragedy?

Thespis (/ˈθɛspɪs/; Greek: Θέσπις; fl. 6th century BC) was an Ancient Greek poet. He was born in the ancient city of Icarius (present-day Dionysos, Greece). According to certain Ancient Greek sources and especially Aristotle, he was the first person ever to appear on stage as an actor playing a character in a play (instead of speaking as themselves). In other sources, he is said to have introduced the first principal actor in addition to the chorus. He is often called the "Inventor of Tragedy".

He is credited with introducing a new style in which one singer or actor performed the words of individual characters in the stories, distinguishing between the characters with the aid of different masks.

This new style was called tragedy, and Thespis was the most popular exponent of it.