DC Comics has produced many crossover stories combining characters from different series of comics. Some of these are set in the fictional DC Universe, or any number of settings within the DC Multiverse.
Crisis and Beyond
Suicide Squad: The Janus Directive
Batman: A Lonely Place of Dying
End of an Era
The Way of the Warrior
The Flash: Dead Heat
The Final Night
Genesis
DC One Million
Superman: Behold! The Millennium Giants!
JLA/Titans: The Technis Imperative
Day of Judgment
JLApe: Gorilla Warfare!
The Flash: Chain Lightning
Superboy: The Evil Factory
Our Worlds at War
Joker: Last Laugh
Bruce Wayne: Fugitive
A World Without Young Justice
JSA: Black Reign
Identity Crisis
Infinite Crisis
Amazons Attack
Sinestro Corps War
Final Crisis
Superman: New Krypton
Batman: The Return of Bruce Wayne
New 52
Batman: Night of the Owls
The Culling: Rise of the Ravagers
Green Lantern: Rise of the Third Army
Rotworld
Hawkman: Wanted
The Black Diamond Probability
Batman: Death of the Family
Superman: H’El on Earth
Justice League: Throne of Atlantis
Batman: Requiem
Superman: Psi War
Batman: Zero Year
Justice League: Trinity War
Forever Evil
Green Lantern: Lights Out
Supergirl: Red Daughter of Krypton
Batman: Gothtopia
Worlds Finest: First Contact
Superman: Doomed
Green Lantern: Uprising
Batman: Endgame
Green Lanterns/New Gods: Godhead
The New 52: Futures End
Earth 2: World’s End
Convergence
Truth
Darkseid War
Robin War
The Savage Dawn
The Final Days of Superman
Rebirth
Batman: Night of the Monster Men
Justice League vs. Suicide Squad
Superman Reborn
Batman/The Flash: The Button
The Lazarus Contract
Dark Nights: Metal
Doomsday Clock
Super Sons of Tomorrow
Milk Wars
The Wedding
Sink Atlantis
The Witching Hour
Drowned Earth
Leviathan Rising
The Terminus Agenda
Year of the Villain
Joker War
Dark Nights: Death Metal
Endless Winter
More Stories
Trinity Reading Order
Superman: Fall of Metropolis Reading Order
The Infinity Stones are BACK