Cast
David Harbour as Hellboy / Anung Un Rama: A powerful demon who works for the government organization Bureau for Paranormal Research and Defense (B.P.R.D.). Harbour was suggested for the role by Mignola after having seen his work on Stranger Things. Harbour stated that the film would be a "character piece" and feature mature themes and "complicated subjects" that warrant the film's R-rating, stating, "It really is this study of this man going through this horrible conundrum and we really get to go in deep with him." Mignola stated that Harbour had been researching the character, adding, "He's texting me Hellboy questions about his history, about what the character would think about this or about that." Mignola described Harbour's Hellboy as being more dramatic, gritty, and emotionally explosive than Perlman's. Harbour refrained from imitating Perlman's Hellboy by depicting his own version similar to a "teenager," describing him as "younger" and "rougher," stating, "He's really struggling with the idea of whether or not he's a good person."
Milla Jovovich as Vivienne Nimue, the Blood Queen: A powerful British sorceress from the Dark Ages, who seeks to annihilate humanity. Harbour had stated that Hellboy has a "very special relationship" with Nimue and that the film expands her role from the comics. Jovovich described the character as being "literally the queen of the underworld," serving as the mother of the monsters, and described Nimue's plan as "beautiful" and "relevant" to today's political climate in trying to bring people together.
Ian McShane as Professor Trevor "Broom" Bruttenholm: Hellboy's adoptive father and the founder of the B.P.R.D. He, Satton, and Lord Glaren of the Osirus Club were given decelerated aging by a powerful spirit through a seance that made them aware of the potential threat that Hellboy posed. Harbour stated that their version of Bruttenholm is a much harder character who does not sympathize with Hellboy questioning his place in the world.
Sasha Lane as Alice Monaghan: A young woman of part Irish descent, who became a powerful medium after she was kidnapped by fairies as a baby. Harbour stated that the character "gets to play with some really interesting ideas of, sort of, being a witch and having visions".
Daniel Dae Kim as Ben Daimio: An M11 military and agent member of the B.P.R.D. who, due to a supernatural encounter, can turn into a terrifying werejaguar when angered or in pain and uses injections to suppress the transformations. Ed Skrein was originally cast in the role but upon discovering that Daimio was portrayed in the comics as Japanese-American, he withdrew to allow an Asian actor to be cast instead. A month later, Kim was cast in the role.
Stephen Graham (voice) and Douglas Tait (on-set; uncredited) as Gruagach: A pig-like fairy who restored Nimue to exact revenge on Hellboy. Graham provides the voice for Gruagach while Tait provides the physical performance.
Sophie Okonedo as Lady Hatton: A resident seer at the Osiris Club, an ancient English club dedicated to uncovering supernatural mysteries.
Alistair Petrie as Lord Adam Glaren: A high-ranking member of the Osiris Club.
Brian Gleeson as Merlin: An ancient and powerful sorcerer, a figure of Arthurian legend.
Penelope Mitchell as Ganeida: An elder witch who has decided that Nimue's wrath has gone on for too long and must be stopped.
Mark Stanley as King Arthur: The ruler of Camelot who is based on the figure of Arthurian legend.
Thomas Haden Church as Lobster Johnson: A vigilante with a violent reputation as he killed mobsters and Nazis while burning his trademark lobster claw symbol into their foreheads with the palm of his gloved hand.
Emma Tate (voice) and Troy James (on-set) as Baba Yaga: A one-eyed Russian witch who lives in a chicken-leg house, having lost her right eye to Hellboy in the past. Tate provides the voice for Baba Yaga, while James provides the on-screen performance.
Additionally, Mario de la Rosa plays Esteban Ruiz / Camazotz, Ava Brennan and Anthony Delaney play Alice's mother and father, respectively. Atanas Srebrev and Dawn Sherrer appear as Agent Madison and Agent Strode, respectively, while Markos Rounthwaite plays Grigori Rasputin and Vanessa Eicholz appears as Ilsa Hepstein. Ilko Iliev plays Professor Doctor Karl Ruprect Kroenen, Joel Harlow portrays Von Krupt, Dimiter Banenkin plays Leopold Kurtz, and Kristina Klebe portrays Leni Riefenstahl.