- Victor Garber as Professor Martin Stein/Firestorm
- Brandon Routh as Dr. Ray Palmer/The Atom
- Caity Lotz as Captain Sara Lance/White Canary
- Franz Drameh as Jefferson "Jax" Jackson/Firestorm
- Maisie Richardson-Sellers as Amaya Jiwe/Vixen
- Nick Zano as Dr. Nate Heywood/Steel
- Amy Pemberton as Gideon
- Dominic Purcell as Mick Rory/Heat Wave
- Neal McDonough as Damien Darhk
- Tala Ashe as Zari Adrianna Tomaz
- Arthur Darvill as Rip Hunter
- Wentworth Miller as Leonard Snart/Captain Cold 
- Tracy Ifeachor as Kuasa Jiwe
- Jes Macallan as Special Agent Ava Sharpe
- Courtney Ford as Eleanor Darhk
"After the defeat of Eobard Thawne and his equally nefarious Legion of Doom, the Legends face a new threat created by their actions at the end of last season. In revisiting a moment in time that they had already participated in, they have essentially fractured the timeline and created anachronisms – a scattering of people, animals, and objects all across time! Our team must find a way to return all the anachronisms to their original timelines before the time stream falls apart. But before our Legends can jump back into action, Rip Hunter and his newly established Time Bureau call their methods into question. With the Time Bureau effectively the new sheriffs in town, the Legends disband – until Mick Rory discovers one of them in the middle of his well-deserved vacation in Aruba. Seeing this as an opportunity to continue their time traveling heroics, Sara wastes no time in getting the Legends back together."
"We reunite with billionaire inventor Ray Palmer, the unconventional historian-turned-superhero Nate Heywood, and Professor Martin Stein and Jefferson “Jax” Jackson, who together form the meta-human Firestorm. Once reunited, the Legends will challenge the Time Bureau’s authority over the timeline and insist that however messy their methods may be, some problems are beyond the Bureau’s capabilities. Some problems can only be fixed by Legends."
Confirmed plot points
- There will be a four-way crossover with Supergirl, The Flash, and Arrow.
- The crossover will take place over two nights and will consist of 2 "two-hour miniseries". The first "two-hour miniseries" will consist of Supergirl and Arrow while the second one will consist of The Flash and DC's Legends of Tomorrow.
- The crossover will have high emotional stakes and emotional payoffs with romance in the air.
- The title of the crossover is Crisis on Earth-X.
- The Legends are going to be shaken up again as they were at the start of season 2 with new members on the Waverider.
- Zari Adrianna Tomaz will join the Waverider crew.
- A new hero, not original to the show, but not from the comics and not from any of the other DC Arrowverse shows, will appear.
- Rip Hunter will create a new organization known as the Time Bureau.
- The Legends will need to return all anachronisms to their original timelines before the time stream falls apart instead of fixing Aberrations like in Season 2.
- Damien Darhk, Leonard Snart, and Rip Hunter will return. Darhk will be a series regular while the other two will be recurring.
- The version of Snart that will be a "bizarro" version.
- Season 3 will introduce the animated Vixen series' foe Kuasa; EP Phil Klemmer would also like to have some non-human villains on the show.
- Sara Lance will possibly be getting a new love interest.
- There is a very good chance fans will meet Ray’s brother Sydney this season, to also be played by Brandon Routh.
- Episode 4 will head to the 80s to investigate Ray Palmer’s childhood.
- Guggenheim revealed that they've had "really good conversations" with Matt Ryan to reprise his role as Constantine on Legends, but for now, the actor is busy with other projects.
- Damien Darhk will be resurrected from his death in Season 4 of Arrow to lead a team of supernatural villains which will include Grodd and Kuasa.
- Simon Merrells has been cast as Julius Caeser.
- Susie Abromeit has been cast as Ray's mother.
- Eleanor Darhk, the daughter of Damien Darhk will be a recurring character and is being played by Courtney Ford.
- B'wana Beast, a hero from the comics will be introduced this season.
Confirmed new characters
- Zari Adrianna Tomaz: A Muslim-American woman from the year 2030 who lives in a world of contradictions - technology has brought about an incredible change in her future, but too bad human nature hasn't kept pace. Fear, prejudice and a lack of care for the planet have forced Zari to become a "gray hat hacktivist". Described as a computer nerd with a wry, combative attitude, she is a woman living a double life who doesn’t realize that she has secret, latent powers derived from an ancient, mystical source.
- P.T. Barnum: A larger-than-life showman, who founded Barnum & Bailey Circus (aka "The Greatest Show on Earth").
- Special Agent Ava Sharpe: An "incredibly ambitious" member of a secret government bureau dedicated to protecting history and regulating time travel.
- Julius Caesar:
- Eleanor Darhk: Cunning with a charming dose of otherworldly creepiness, she possesses the uncanny ability to manipulate others.
- B'wana Beast:
|#||Episode name||Directed by||Story by||Teleplay by||Original airdate|
|1||"Aruba-Con"||Rob Seidenglanz||Phil Klemmer & Marc Guggenheim||October 10, 2017|
|2||"Freakshow"||Kevin Tancharoen||Keto Shimizu & Grainne Godfree||TBA|
|3||"Zari"||Mairzee Almas||James Eagan & Ray Utarnachitt||TBA|
|4||"Phone Home"||Kevin Mock||Matthew Maala||TBA|
|5||"Return of the Mack"||Alexandra La Roche||Grainne Godfree & Morgan Faust||TBA|
|6||"Helen Hunt"||David Geddes||Keto Shimizu & Ubah Mohamed||TBA|
|7||"Welcome to the Jungle"||Mairzee Almas||Ray Utarnachitt & Tyron B. Carter||TBA|
- ↑ 1.0 1.1 1.2 CW Loads Up Fall Schedule Rollout Across One Week in October - Variety
- ↑ The CW renews seven series including 'Arrow,' 'The Flash,' 'Supernatural' and 'Crazy Ex-Girlfriend' - LA Times
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 New 'Legends of Tomorrow' season 3 details released - Entertainment Weekly
- ↑ New art for @TheCW_Legends #Season3! #LegendsOfTomorrow - Brandon Routh (@BrandonJRouth) Twitter
- ↑ #Phxcc first to know that Neal McDonough signed on for another year of Legends of Tomorrow! - Phoenix Comicon (@PhoenixComicon) Twitter
- ↑ 6.0 6.1 6.2 Legends of Tomorrow: Snart and Darhk Return, Arthur Darvill Now Recurring - TVLine
- ↑ 7.0 7.1 7.2 ‘DC’s Legends of Tomorrow’ Adds Muslim-American Superhero for Season 3 - Variety
- ↑ 'Legends of Tomorrow' Season 3 Will Include Rip Hunter - ScreenRant
- ↑ 9.0 9.1 9.2 9.3 9.4 9.5 Legends of Tomorrow @ Comic-Con: Dino Fights, Revisited Bisexuality and... Constantine? — Plus, Watch Trailer - TVLine
- ↑ 'Legends of Tomorrow' - Season 3 - Tracy Ifeachor Cast as Kuasa - SpoilerTV
- ↑ 11.0 11.1 Legends of Tomorrow Enlists Mistresses Star for 'Ruthless' Season 3 Role - TVLine
- ↑ 12.0 12.1 12.2 'Legends of Tomorrow': Courtney Ford to Recur as (Spoiler)'s Daughter - TVLine
- ↑ 'The Flash' nixes speedster villain in season 4 - EW
- ↑ 14.0 14.1 CW sets two-night event for four-way superhero crossover - Entertainment Weekly
- ↑ Arrowverse Crossover: (Spoiler)'s Wedding Confirmed in Key Art - TVLine
- ↑ 16.0 16.1 Season 3 Of Legends Of Tomorrow Gets A Unique New Hero To The Crew - Bleeding Cool
- ↑ 17.0 17.1 'DC'S Legends of Tomorrow': Season 3's Supernatural Villian Recruits Gorilla Grodd - IGN
- ↑ 18.0 18.1 TVLine Items: Shameless Return Date, DC's Legends Hails Caesar and More - TVLine
- ↑ 'Legends of Tomorrow': Jessica Jones' Susie Abromeit Cast as Ray's Mom - TVLine
- ↑ 20.0 20.1 First Look at B'wana Beast on Legends of Tomorrow - Comicbook.com
- ↑ 'Legends of Tomorrow' casts Billy Zane as P.T. Barnum - Entertainment Weekly
- ↑ 22.0 22.1 22.2 Marc Guggenheim (@mguggenheim) - Twitter
- ↑ 23.0 23.1 23.2 Marc Guggenheim (@mguggenheim) - Twitter
- ↑ 24.0 24.1 24.2 Marc Guggenheim (@mguggenheim) - Twitter
- ↑ 25.0 25.1 25.2 Marc Guggenheim (@mguggenheim) - Twitter
- ↑ 26.0 26.1 26.2 Marc Guggenheim (@mguggenheim) - Twitter
- ↑ 27.0 27.1 27.2 Marc Guggenheim (@mguggenheim) - Twitter
- ↑ 28.0 28.1 28.2 Marc Guggenheim (@mguggenheim) - Twitter
|DC's Legends of Tomorrow season 3|
|"Aruba-Con" • "Freakshow" • "Zari" • "Phone Home" • "Return of the Mack" • "Helen Hunt" • "Welcome to the Jungle" • TBA|