Updated December 28, 2018: A caption from an official image on Disney's Captain Marvel movie homepage identifying Jude Law's previously unnamed character as Mar-Vell has been removed. The image, which remains on the site, now simply names Law's character "Leader of the Starforce."
The change happened quietly, so it's unclear if the original caption was written in error, or if Law's reveal as Mar-Vell was meant to remain a surprise.
There is another possibility, that the image and its sudden removal are intended to keep fans confused and guessing about the character's identity. Marvel Studios is not above purposeful misdirection in its marketing - i.e. the Hulk appearing in the Wakanda scenes in Avengers: Infinitiy War trailers.
For that reason we still believe Law actually might be ALL of the characters various marketing materials have identified him as.
Here's a screenshot of the image with the updated caption. A screenshot of the removed caption can be seen in the original report below.
Original Story: Jude Law's unidentified character in Captain Marvel has officially been named - and he's playing Mar-Vell, the Kree warrior who, in comic books, preceded Carol Danvers as Captain Marvel.
The identity of Law's character was confirmed in the caption for a photo of Law on Disney's official Captain Marvel homepage, as seen in the screenshot below:
Law's character's identity has been in question for some time, with various unconfirmed sources identifying him as both Mar-Vell and Yon-Rogg at different times.
In comic books, Mar-Vell is a Kree warrior who becomes a protector of Earth after being betrayed and left for dead. His relationship with Carol Danvers led to her assuming the Ms. Marvel identity and eventually becoming Captain Marvel.
In the film, Mar-Vell has been identified as a "devout Kree warrior" who is the leader of Starforce.
Of course, there's always the chance there's more to this than meets the eye, as laid out in Newsarama's theory about his identity, right here.
Captain Marvel is due out in theaters March 8.