Series overview
Season 123456
"You are no god. Just as I am no devil. All I am is truth. And judgement. And death. And I will reign."
Reign to Supergirl[src]

The third season of Supergirl​​​​​ premiered on October 9, 2017 on The CW and concluded on June 18, 2018. The season consisted of 23 episodes.


Main cast

Recurring cast



# Episode name Directed by Story by Teleplay by Original airdate
1 "Girl of Steel" Jesse Warn Andrew Kreisberg Robert Rovner & Caitlin Parrish October 9, 2017
Kara deals with the loss of Mon-El by focusing all her energy on being Supergirl and the mysterious new threat against National City. Alex confesses a secret to Maggie about their impending nuptials. A citizen of National City has a mysterious connection to Kara, and Lena Luthor makes a bold move.
2 "Triggers" David McWhirter Gabriel Llanas & Anna Musky-Goldwyn October 16, 2017
Psi, a thief with psychic powers, attacks National City. Able to immobilize people by tapping into their worst fears, Psi proves a formidable opponent for Supergirl. Meanwhile, James Olsen and Lena Luthor are at an impasse, and Samantha starts her new job at L-Corp.
3 "Far From the Tree" Dermott Downs Jessica Queller & Derek Simon October 23, 2017
Eliza throws Alex and Maggie a wedding shower, which causes Maggie to reach out to her estranged father. Supergirl joins J'onn on a personal mission.
4 "The Faithful" Jesse Warn Paula Yoo & Katie Rose Rogers October 30, 2017
Kara investigates a secretive new group whose leader, Thomas Coville, has a mysterious connection to Supergirl. Meanwhile, Samantha feels like she's letting Ruby down, and J'onn confesses an old secret.
5 "Damage" Kevin Smith Eric Carrasco & Cindy Lichtman November 6, 2017
When multiple children get sick from lead poisoning, Morgan Edge points the finger at Lena and blames her creation of the lead bomb she made to save National City from the Daxamites. While Lena knows she never intended any harm, she fears there may have been a flaw in her design, leaving her responsible. Kara teams up with Samantha to clear Lena's name, but it turns out to be harder than they thought. Meanwhile, Alex and Maggie make a crucial decision about the future of their relationship.
6 "Midvale" Rob Greenlea Caitlin Parrish & Jess Kardos November 13, 2017
Kara and Alex head home to Midvale for a little R&R. While there, Kara recalls a painful memory of a childhood friend's death and how that traumatic experience brought the Danvers sisters closer together.
7 "Wake Up" Chad Lowe Gabriel Llanas & Anna Musky-Goldwyn November 20, 2017
When Winn and the team discover an alien ship has crash landed deep underwater beneath National City, Kara/Supergirl is called in to investigate. Meanwhile, Hank attempts to bond with his father, Myr’nn. Samantha, eager for some understanding of the changes she has been experiencing, looks to her estranged mother, Patricia Arias, for answers.
8 "Crisis on Earth-X, Part 1" Larry Teng Andrew Kreisberg & Marc Guggenheim Robert Rovner & Jessica Queller November 27, 2017
Barry and Iris's wedding brings the gang together, but things go awry when villains from Earth-X attack the ceremony. All of the superheroes band together with help from their super friends like Citizen Cold, The Ray, Felicity Smoak, Iris West and Alex Danvers to take on their most formidable villains yet. Earth's mightiest heroes – Green Arrow, Supergirl, The Flash and White Canary – lead their teams into battle to save the world.
9 "Reign" Glen Winter Paula Yoo & Caitlin Parrish December 4, 2017
Supergirl investigates a mysterious symbol popping up all over National City, tracing its origins back to an ancient prophecy and the mark of the World Killer, Reign. Meanwhile, the tension between Lena and Morgan Edge continues to build, causing James to step in and offer up some protection, and possibly igniting a spark in the process.
10 "Legion of Super-Heroes" Jesse Warn Derek Simon & Eric Carrasco January 15, 2018
Struggling to heal from her injuries inflicted by Reign, Supergirl remains in a dreamlike state, unable to be reached. Mon-El recruits one of The Legion members, Brainiac-5, to try to bring her back. Meanwhile, Reign continues her rampage on the city so the DEO teams up with the Legion of Superheroes to try to stop her.
11 "Fort Rozz" Gregory Smith Gabriel Llanas & Anna Musky-Goldwyn January 22, 2018
As Reign continues to terrorize the city, Supergirl teams up with Saturn Girl, and the two recruit Supergirl's former enemies, Livewire and Psi, to form a team for a mission to Fort Rozz to recover a prisoner who has information on how to defeat Reign once and for all. Meanwhile, Alex babysits Ruby.
12 "For Good" Tawnia McKiernan Robert Rovner Cindy Lichtman & Alix Sternberg January 29, 2018
Someone tries to kill Morgan Edge and he barely survives. He accuses Lena of being behind the attempt and vows to destroy her. When Lena fears her hatred for Morgan will take her to the Luthor dark side, Kara steps in to help her friend. Meanwhile, after Sam realizes she's losing time, she confides in Alex who decides to run some medical tests to see if she can find out what's going on with her new friend.
13 "Both Sides Now" Jesse Warn Jessica Queller & Paula Yoo February 5, 2018
The DEO captures a second World killer, Purity. Supergirl and Alex use very different methods of interrogation with Purity in the hopes of finding out how to defeat Reign. However, Purity escapes and attacks the city's subway tunnels. Meanwhile, J'onn, Winn and Mon-El band together to fix the Legion ship.
14 "Schott Through the Heart" Glen Winter Caitlin Parrish & Derek Simon April 16, 2018
When Winn's father dies, his estranged mother, Mary, reappears trying to reconnect and to explain why she abandoned him all those years ago. Winn is too embittered from his rough childhood to forgive her but when a copycat Toymam attacks, the two must work together to stop him. Mon-El tells Kara something important about the Worldkillers, and Alex becomes suspicious of M'yrnn's recent behavior.
15 "In Search of Lost Time" Andi Armaganian Eric Carrasco Katie Rose Rogers & Nicki Holcomb April 23, 2018
M'yrnn inadvertently causes psychic disturbances at the DEO; Supergirl must work with J'onn to contain the chaos; Mon-El begins training Kara in fighting techniques he's learned in the future.
16 "Of Two Minds" Alexandra La Roche Gabriel Llanas & Anna Musky-Goldwyn April 30, 2018
Supergirl and Imra have different ideas on how to stop the third world killer, Pestilence. However, when both Alex and Winn are seriously injured by Pestilence, Supergirl and Imra team up to stop the destruction.
17 "Trinity" Caitlin Parrish & Jesse Warn Jessica Queller Caitlin Parrish & Derek Simon May 7, 2018
Still reeling after learning about Lena's secret, Supergirl asks Guardian for a favor that could alter his relationship with Lena forever. Meanwhile, with all three Worldkillers united, Supergirl and the team brace for an epic battle.
18 "Shelter from the Storm" Antonio Negret Robert Rovner Lindsay Gelfand & Allison Weintraub May 14, 2018
When Reign starts hunting Ruby, Supergirl and Alex work together to keep her safe. Supergirl and J'onn look to Sam's mother for advice on how to stop Reign and come away with some shocking news.
19 "The Fanatical" Mairzee Almas Paula Yoo & Eric Carrasco May 21, 2018
When Tanya, a disciple of Coville's, escapes from what's left of his cult, she gives Kara and James a journal that could hold the key to saving Sam. Someone learns Guardian's identity and threatens to expose James if he doesn't do what they ask. James contemplates what it means to be a black vigilante without a mask in America.
20 "Dark Side of the Moon" Hanelle Culpepper Derek Simon & Katie Rose Rogers May 28, 2018
Supergirl is stunned to discover that a part of Krypton survived. Meanwhile, Alex is attacked while out with Ruby, and Lena considers how far she will go to keep Reign contained.
21 "Not Kansas" Dermott Downs Gabriel Llanas & Anna Musky-Goldwyn June 4, 2018
Kara makes a major life decision. Meanwhile, J'onn finds out that special DEO-caliber guns have hit the streets of National City.
22 "Make it Reign" Armen V. Kevorkian Ray Utarnachitt & Cindy Lichtman June 11, 2018
After learning the true depth of Selena's nefarious plans for Earth, Supergirl, Mon-El and Alura must come up with a plan to stop her. J'onn prepares to say goodbye to his father.
23 "Battles Lost and Won" Jesse Warn Robert Rovner & Jessica Queller June 18, 2018
Supergirl and team take on Selena in an epic battle for Earth.


  • Starting this season, the title card changes to match the theme of the season.


Title cards

Promotional images



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