Joaquin Phoenix has agreed to play the Joker in writer/director Todd Phillips' untitled Joker origin film produced by Martin Scorcese, according to Variety. the Hollywood trade said that Phoenix was approached as Phillips' top choice for the role in late 2017, and agreed to it - although "studio negotiations" have not commenced.
Phillips' Joker film is said to "delve into what it took for the Joker to become a mastermind criminal," and take place in the 1980s.
This film is framed as part of an unnamed new banner within Warner Bros' DC Films division that are out-of-continuity with its primary DC Extended Universe stories - such as Justice League or, in this case, Suicide Squad.
Jared Leto is still expected to play the Joker in DC Films' planned Suicide Squad sequel.
This would be Phoenix's third flirtation with a major superhero hero - he was rumored to have been courted to play Marvel Studios' Doctor Strange years ago, and THR says he turned down the role of Lex Luthor in Batman v Superman: Dawn of Justice.