Flip monsters (Japanese: リバースモンスター Ribāsumonsutā "Reverse Monster"), formerly Flip Effect Monsters (リバース
Previously, Flip Effects (as they were capitalized at the time) were a type of card effect like Trigger and Ignition Effects, with Flip Effects being able to be identified by the text "FLIP:" at the start of the effect; Flip Effect Monsters were simply monsters that had a Flip Effect. Starting in Starter Deck 2014 (in the OCG) and Super Starter: Space-Time Showdown (in the TCG), Flip is treated as an ability and the word "Flip" is written on the cards' Type/Ability line.
A Flip effect is a type of Trigger Effect that is preceded by "FLIP:". This kind of effect meets its activation timing when the Flip monster on the field is flipped from face-down to a face-up, even during the Damage Step.
Some monsters have effects with the timing "when this card is flipped face-up" (unofficially called Pseudo-Flip Effects), such as "Snowman Eater", which, while mechanically identical, are distinct from Flip effects.
When a face-down Flip monster is attacked, during damage calculation the monster is flipped face-up, then it is determined whether or not the monster is destroyed by battle. During the Damage Step, after damage calculation but before being sent to the Graveyard if it was destroyed by battle, the Flip monster's Flip effect activates and resolves on the field, if the timing is correct.
- There are currently no Dragon, Dinosaur, or Fish-Type Flip monsters.
- Flip monsters are rarely used in the anime; in the anime, prior to Yu-Gi-Oh! ZEXAL, it was legal to Normal Summon a monster in face-up Defense Position, and monsters were rarely Set.
- "Performapal Momoncarpet" is the only Pendulum Flip monster.
- The only characters to have a Deck based on Flip monsters are (the appropriately-named) Flip Turner from Yu-Gi-Oh! ZEXAL and Aura Sentia from Yu-Gi-Oh! ARC-V.
- "Subterror Behemoth Ultramafus" has the highest Level and original ATK of all Flip monsters, being Level 12 with 3000 ATK.
- "Pot of The Forbidden" has the highest DEF of all Flip monsters, with 3000 DEF.
- The illegal card "Masahiro the Dark Clown" is the only Flip monster to have flavor text.