Released by Vulture, the image expands on the dark turn taken by Nucky (Steve Buscemi) in the second season finale, which saw him murder one-time protégé and surrogate son Jimmy (Michael Pitt).
The season tagline "You can't be half a gangster" echoes a line of dialogue spoken by Jimmy to Nucky in the show's pilot, and was previously used in the first trailer for the season.
Buscemi, Kelly McDonald, Michael Shannon, Michael Kenneth Williams, Gretchen Mol and Jack Huston are among the show's returning cast members, while Bobby Cannavale joins the cast as a charismatic but ruthless gangster.
The third season of Boardwalk Empire will debut on September 16 on HBO in the US, and September 29 on Sky Atlantic in the UK
See a selection of first-look photographs from the new season below: