Jared Leto is the Joker of the DCEU films, as established in SUICIDE SQUAD, but while Warner Bros. claims that they'll be making a Leto Joker movie somewhere down the line, they have also given the greenlight to a JOKER film that will exist outside the DCEU – that is, in a different universe than SUICIDE SQUAD, MAN OF STEEL, BATMAN V. SUPERMAN, WONDER WOMAN, and JUSTICE LEAGUE.
Directed by THE HANGOVER's Todd Phillips from a screenplay he has written with Scott Silver, the JOKER movie will star Joaquin Phoenix as the title character and is said to be a dark character study in the vein of TAXI DRIVER and THE KING OF COMEDY.
With the project moving toward a September production start, it looks like Phoenix is set to get his first co-star: Zazie Beetz, who recently played the Marvel Comics character Domino in DEADPOOL 2, is in talks to play
a single mother who catches the interest of the man who will become the "clown prince of crime."
I'm not sure about this project yet; I am very interested to see what a Joaquin Phoenix Joker will be like, but I'm wary of the idea of the Joker carrying his own movie.
JOKER reportedly has a budget in the $55 million range and is scheduled to be released on October 4, 2019.