Season 4 (Supergirl)

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

Main cast

 * Melissa Benoist as Kara Danvers/Supergirl and Kara Danvers
 * 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 Colonel Lauren Haley
 * David Harewood as J'onn J'onzz

Special guest cast

 * Lynda Carter as Olivia Marsdin
 * 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
 * LaMonica Garrett as Mar Novu/The Monitor
 * Xander Berkeley as Peter Lockwood
 * TBA as Lex Luthor
 * Azie Tesfai as Kelly Olsen

Confirmed plot points

 * There will be an Elseworlds 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.
 * Lex Luthor will be introduced this season with casting underway.
 * James Olsen's sister will appear this season.

Confirmed new characters

 * Lois Lane: Described as the daughter of U.S. 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.
 * Mar Novu/The Monitor: An extraterrestrial being of infinite power.
 * 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.
 * Lex Luthor: He will shake things up in National City and go toe to toe with not only Supergirl, but his sister Lena Luthor.
 * Kelly Olsen: Kelly is an intelligent and insightful woman who spent time in the military in order to pay for medical school. She's recently discharged from the military and is currently finishing her training as a psychiatrist. She's got a large heart and cares deeply about others.

Trivia

 * This season airs 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.