For the first two seasons of this show (Justice League), the storyline focused on the seven founding members:
- J'onn J'onzz as Martain Manhunter
- Clark Kent/Kal-El as Superman
- Princess Diana as Wonder Woman
- Bruce Wayne as Batman
- John Stewart as Green Lantern
- Shayera Hol as Hawkgirl
- Wally West as The Flash
The last three seasons showed a variety of other DC heroes which included Green Arrow, Aquaman, The Atom, Captain Atom, Mister Terrific, Supergirl, Wildcat, Zatanna, and many more. The League also consisted of reserve members such as Speedy (Roy Harper) and The Crimson Avenger. As well as nods to rather obscure comic figures like Mordu, and Composite Superman made appearances as well.
Because of the Bat-Embargo to limit or ban the use of Batman related characters from any media source outside of Christopher Nolan's Batman movies and The Batman animated series meant that only more obscure Bat-villains such as the KGBeast, Clock King, Amygdala, Sportsmaster, Blockbuster, Copperhead and Hellhound would appear in the series.
- For the Man Who Has Everything
- Kid Stuff
- Hawk and Dove
- This Little Piggy
- Feaful Symmetry
- The Greatest Story Never Told
- The Return
- Dark Heart
- Wake the Dead
- The Once and Future Thing Part One: Weird Western Tales
- The Once and Future Thing Part Two: Time, Warped
- The Cat and the Canary
- The Ties That Bind
- The Doomsday Sanctum
- Task Force X
- The Balance
- Double Date
- Hunter's Moon
- Question Authority
- Panic in the Sky
- Divided We Fall
- project batman beyond
- I Am Legion
- Shadow of the Hawk
- Chaos at the Earth's Core
- To Another Shore
- Flash and Substance
- Dead Reckoning
- Patriot Act
- The Great Brain Robbery
- Grudge Match
- Far From Home
- Ancient History
- Justice League Unlimited (JLU) is the last show in the DCAU
- There were crossovers with Static Shock and Batman Beyond.
- Michael Rosenbaum, who portrays Lex Luthor on Smallville, also voiced Luthor in the episode The Great Brain Robbery. He also voices Wally West/The Flash.
- In January 2009, IGN dubbed Justice League Unlimited the 20th best animated television series.
Superman: I once thought I could protect the world by myself, but I was wrong. Working together, we saved the planet, and I believe that if we stay together as a team, we could be a force that could truly work for the ideals of peace and justice.
The Flash: What, like a bunch of... super friends? Superman: More like a Justice League. (Secret Origins)
Green Lantern: In brightest day, in blackest night, no evil shall escape my sight. Let those who worship evil's might, beware my power: Green Lantern's light!! (In Blackest Night)
Batman: There's not much time. If we can't shut that down, the entire world is doomed!
Green Lantern: I suppose this is a bad time to say "I told you so." (The Enemy Below)
Wonder Woman: I am Diana, Princess of the Amazons! I won't be denied! (Paradise Lost)
[About Copperhead, who was captured after biting Batman] Superman: I'm going down to interrogate him. Batman: Alright. Let's go.
Superman: No, you're staying here. That venom almost killed you.
Batman: So? (Injustice For All)
Martian Manhunter: I was just thinking...you, me, Wonder Woman, Superman - we are all of us orphans and exiles.
Hawkgirl: Maybe we should call ourselves the "Just Us League." (Twilight)
Batman: Next time I let Superman take charge, just hit me. Real hard. (Twilight)
[Martian Manhunter is using one of Brainiac's bodies as a shield as he shoots at the others.] Batman: Having fun?
Martian Manhunter: Yes. (Twilight)
Princess Audrey: Don't worry - I won't tell anyone that our great hero has feet of clay. Wonder Woman: You have no idea. (Maid of Honor)