Season 4 (Supergirl)

Supergirl was renewed for a fourth season by The CW on April 2, 2018. It will premiere on October 14, 2018.

Main cast

 * Melissa Benoist as Kara Danvers/Supergirl
 * Mehcad Brooks as James Olsen
 * Chyler Leigh as Director Alex Danvers
 * Katie McGrath as Lena Luthor
 * Jesse Rath as Querl Dox/Brainiac 5
 * Sam Witwer as Ben Lockwood/Agent Liberty
 * Nicole Maines as Nia Nal/Dreamer
 * April Parker Jones as Haley
 * David Harewood as J'onn J'onzz

Special guest cast

 * Ruby Rose as Kate Kane/Batwoman
 * Tyler Hoechlin as Clark Kent/Superman
 * Elizabeth Tulloch as Lois Lane

Recurring cast

 * Jeremy Jordan as Winn Schott
 * David Ajala as Manchester Black
 * Rhona Mitra as Mercy Graves
 * Robert Baker as Otis Graves
 * Bruce Boxleitner as Vice President Baker
 * Anthony Konechny as Jensen
 * TBA as Lon-El
 * Xander Berkeley as Peter Lockwood

Confirmed plot points

 * There will be a crossover with The Flash and Arrow. The crossover will introduce Batwoman and Gotham City.
 * Journalism is going to be a big part of the season.
 * The theme of the season is, "What Is Stronger; Hope or Fear?"
 * The Red Son-ish cliffhanger from the Season 3 finale will become a big centerpiece in the latter part of the season.
 * This season, Brainiac will socially butt heads with a couple people.
 * Mehcad Brooks hinted that there will be "fallout" from James choosing to unmask himself as Guardian last season.
 * What will the characters make of Kate Kane aka Batwoman, in this December's Arrowverse crossover? "I think Alex might really like her", EP Sarah Schechter surmised with a smile. "I think strong women like each other, and strong women support each other. They definitely have very different ways of behaving in the world, but I think, ultimately, they'll agree that women should be in charge".
 * David Harewood will direct an episode this season.
 * Brent Spiner was originally cast as Vice President Baker, but had to step down due to a family emergency and was replaced by Bruce Boxleitner.
 * Lynda Carter will return as Olivia Marsdin.

Confirmed new characters

 * Nia Nal/Dreamer: A confident, wunderkind of a fashionista. Once a political speechwriter, Nia is the newest addition to the CatCo investigative reporting team. With her she brings sparkling wit and biting humor but under that banter-y, chic facade, lays a soulful young woman who has much to offer the world. She is also Transgender.
 * Ben Lockwood/Agent Liberty: A businessman whose success has burned down to the ground. Blaming others for his failure and not having his back, he is now making it his life goal to correct those wrongs. Be careful of his dangerous ability to persuade people as he has no problem using that as a method to accomplish his goals. Deeply evil — founder of Children of Liberty, an anti-alien hate group dedicated to establishing humans as the superior race. According to the show’s producers, he conceals his vile nature "in the guise of a family man", making it all the more difficult to take him down.
 * Haley: Her actions make it clear that she is someone you don't want to mess with, without her having to say a word. She is loyal to her commanding officer as well as her country by making sure she puts its best interest ahead of her own.
 * Manchester Black: He's the type of guy who brings a knife to a gunfight and still walks away the winner. With a dark past, he easily deflects the brutality of his mission with his charm and sense of humor.
 * Mercy Graves: An ex-Cadmus agent who has always believed in human exceptionalism. But with both Lex and Lillian in prison, Mercy is stepping out of the Luthor shadow and running her own show. With her biting wit and lethal brawn, Mercy steadily becomes a key figure in National City's growing "human-first" movement.
 * Otis Graves: Mercy's de facto right-hand man. What he lacks in brains, he makes up for with his savant-like abilities to assassinate aliens.
 * Baker: Adept and politically minded, VP Baker makes for an unlikely leader, but steps up in a big way when his country needs him most.
 * Jensen: A rookie DEO agent recruited by Alex Danvers, who struggles to find his footing at the DEO.
 * Lois Lane: Described as the daughter of US General Sam Lane, Lois is a tenacious, righteous and stubborn reporter who will go to any length to get the story and almost never fails.
 * Lon-El: Lon-El is described as a mysterious visitor who is from another planet and is both ambiguous, inscrutable and has the power that is teased as nearly infinite.
 * Peter Lockwood: Ben Lockwood's father. A middle-class factory owner struggling to make ends meet in a world that’s rapidly changing due to the rise of aliens from outer space living amongst us. Proud and single-minded, a family man who’s dedicated his life providing for people. The seeds of his discontent sows the beginning of an anti-alien wave.
 * John Deegan: A doctor at Arkham Asylum for the Criminally Insane in Gotham City, but he might just be crazier than the inmates he treats. His machinations will draw Green Arrow, The Flash and Supergirl to Gotham City.

Trivia

 * This season will air on Sundays at 8/7c, as opposed to the past three seasons, where it aired on Mondays at the same time.
 * Season 4 is the first season to introduce a live-action transgender superhero.