Which actor played the Joker in Batman?

That depends on which "Batman" you're referring to! Here are some of the most famous actors who have played the Joker:

* Cesar Romero (1966-1968) - Played the Joker in the classic "Batman" TV series.

* Jack Nicholson (1989) - Played the Joker in Tim Burton's "Batman."

* Heath Ledger (2008) - Played the Joker in Christopher Nolan's "The Dark Knight."

* Jared Leto (2016) - Played the Joker in David Ayer's "Suicide Squad."

* Joaquin Phoenix (2019) - Played the Joker in Todd Phillips' "Joker."

Let me know which "Batman" you're thinking of and I can give you a more precise answer!