She’s not as early as some mentioned here, but for film stars, she’s pretty early… and I may be mistaken, Eve would be able to best confirm… but wasn’t Alla Nazimova credited as simply ‘Nazimova’ in Salome?
We can probably leave out people that only had one name - I know, I suggested Socrates previously but I’m pretty sure that he, Homer and Pythagoras would not work here. Neither would Spartacus. No last name.
Julius Caesar, however, would, as he is alternately known simply as “Caesar”.
Buddha is an even better example since his real name was (probably mangled by me here…) Gautamma Siddhartha.
Of course, the OP was looking for entertainers, and only Homer and Spartacus can be shoe-horned into that description here…but you guys get it, right? We’re looking for one name when the person would normally have been known by a first and last name - right?
Yep, she was—but since we’d already listed several pre-1900 performers, I didn’t bother bringing her up. Ditto, “Garbo.”