Ring Out

To win a match held in a bounded area by throwing, forcing, or tricking the enemy into stepping out of bounds, thus disqualifying them on a technicality.

Occasionally justified by the rules of the sport - but only a few Real Life sports use it. Another attempt at a Hand Wave is to make the edge of the ring be a Bottomless Pit. The Ring Out Boss is a subtrope of this where a boss in a videogame has to be defeated by a Ring Out.

Anime & Manga

In each Tournament Arc of Dragon Ball, this was a valid way of winning...until the Cell Games, when Cell decides to nuke the ring from orbit so they can keep fighting since Goku's made it so fun to play.
- Note that you have to land outside the ring to be disqualified. And most of the characters in the show can fly.
The Martial Arts Gymnastics tournament in Ranma ½. Notable in that the ring can move on command.
- This is also implied in the Joketsuzoku ("Chinese Amazon") tournament that Ranma interrupted while in China. Getting kicked off the dueling log cost Shampoo the championship, even though she wasn't knocked unconscious.
  - The "woman" she beat just before Ranma ate the prize lost pretty much the same way.
The Tournament Arc of Yu Yu Hakusho has a similar "destroy the ring so you have to fight to the death" moment.
- Though in the Dark Tournament, you have to be outside the ring for ten seconds (or more accurately, ten counts) to be considered out. Most fights end with somebody dead or unconscious anyway because otherwise they can just climb back into the ring. The exception being Kuwabara who spent most of his counts arguing with his teammate in his first fight, and was later tricked into being warped out of the stadium... twice.
Subverted in Eyeshield 21. With only a few seconds left on the clock and with the Devilbats behind, they have to force themselves out of the field in order to stop the clock. In one special case, Monta used his catching skills to grab the out of bounds and stop the clock.
- The above spoiler is a valid tactic in American football in order to stop the clock.

Live Action--Film

In Ip Man, the final fight against General Miura is held on a raised platform with falling off it as a defeat condition. In the sequel, Ip has to take challenges from the other Hong Kong-based masters on a table, with getting off the table as one of the defeat conditions.
In Bloodsport and its sequels, knocking or forcing your opponent off the raised fighting platform is an Instant Win Condition.

Live Action TV

American Gladiators had this as half of the two-part 'Breakthrough and Conquer' event. The 'Conquer' half required the player to force his or her Gladiator opponent out of a round wrestling-style ring within the alloted 30 seceonds. This was probably toughest and often funniest when the female contenders were trying to do it to six-foot tall Sky.

Professional Wrestling

The Battle Royal, where you must toss your opponents out of the ring (over the top rope only) to win. And there are a lot of variations on it (WWE's Royal Rumble, where the entrants enter in sequence, is probably the most well known).

Video Games

Every 3D Fighting Game, with some exceptions, have implemented this:
- Virtua Fighter. In later installments you have to smash a wall or two first; in the first few installments, before Edge Gravity, it was very easy to ring yourself out by mistake.
- Mortal Kombat: Deadly Alliance, Mortal Kombat: Deception and Mortal Kombat Armageddon. Sometimes the Ring Out will just result in the battle moving to a different stage. In the two latter games, some of those stages have Death Traps, so pushing the character to the bounds meant that they lost the round.
- Soul Calibur. Subverted in 3's Chronicles of the Sword mode where ring outs still exist, but don't kill the person. Instead, it inflicts their max HP worth of damage. Also, averted with Night Terror, who will just fly back into the ring.
Dragon Ball Z: Budokai, although only on a stage based on the World Martial Arts Tournament ring.
Jump Super Stars lets you get a KO by knocking someone out of the "panels" (after bashing your way through the side of the page).
The Legend of Zelda: Twilight Princess has a sumo minigame in which you have to push your Goron opponent out of bounds to win.
- Oracle of Seasons has something similar in a boxing match.
While you can toss objects and enemies out of bounds in Phantom Brave and Makai Kingdom, doing so to enemies just increases the remaining enemy levels by the same amount of the monster that was tossed. Any of your allies that get the same treatment, however, are just gone from the field for the remainder of the battle.
In Super Smash Bros., this is the ONLY way to win (except in Coin Mode; Melee and Brawl also have an Hit Point-based Stamina Mode that simulates the traditional beat-em-up fighting style).
In Def Jam: Fight For New York, there are a couple stages with ring out potential. But you have to smash the ring barriers with the opponent's face a few times in order to get them through. Then there's the Subway stage, where a Ring Out is only an instant win if a train is coming.
The Japanese Genesis game Aah Harimanda is all about sumo wrestling, and, well, the goal is to get the opponent out of the ring.
Averted in the Dead or Alive series; leaving the main section of an arena will frequently cause damage, but the game will still continue until one character is knocked out normally.
Each stage of Real Bout Fatal Fury (except Geese Tower) had destroyable boundaries at the edges. Getting knocked out (or falling out on your own) rewarded your opponent with a special animation as well as the win for the round.
Battle Arena Toshinden (with the additional Good Bad Bug of the victor being able to fall out of the ring themselves during their Victory Pose). In fact, beating the game on a two-day rental was a fairly mean feat if you once figured out the knack for performing the Ring Out trick even up to and on the final boss.
Dark Messiah has a kick attack that can send enemies flying a good distance. The game's environments are built in such a way that this move can be more devastating than the best spells or weapons, to the point where 1UP.com dubbed it "The Adventures of Sir Kicksalot Deathboot in the Land of the Conspicuously Placed Spike Racks".
This is how King Hippo is KOed in Punch-Out!! Wii.
The bosses of Castles 1 and 7 in Super Mario World can only be defeated by knocking them off the platform into the surrounding Lava Pit.
- Similarly, Bullies and Big Bullies in Super Mario 64 (DS) can only be defeated in the same way.
- Inverted in Super Mario 64 with Big Bob-omb. Throwing him off his mountain will restart the battle from the beginning.
In the Bloody Roar series, you can choose to have walls around the arena or not; and if you have walls turned on, you can choose whether they're breakable or not. In either case, if you leave the ring, it's an automatic victory for the other player.
One stage in Brutal Paws Of Fury is a bridge from which you can knock your enemies off.
In the arena fights with the handmaidens and Mandalorians in Knights of the Old Republic II where you are allowed to use the Force, using one of the Force Push line of powers to knock the opponents out of the ring automatically disqualifies them.
One fight in King's Quest Mask of Eternity can only be won by knocking your opponent off of the tower you're fighting on.
In something like an inversion of Ledge Bats, Kratos can ring out some of his enemies by physically dragging or throwing them across the invisible line that marks their A.I. boundary, while he himself has no such artificial boundaries and is protected against normal pits by Edge Gravity (even when Blown Across the Room).
The rooftop levels in most Twisted Metal games.
The latest game titled Prince of Persia has this. It's how 90% of the mooks are likely to die, given how block-happy they are, and a good way to kill The Hunter. Beating The Warrior tends to require you do this, as well.
Magicka. A lot of the spells have more than a little kick to them.
One of the stadia in Carmageddon is a giant tower and you can ram your opponents over the edge. Technically this doesn't result in an automatic write off as it is just possible to have your car sufficiently powered up to survive the resulting damage, but it is almost impossible to return from without restarting.
The original Mass Effect had open areas where this was a viable strategy. A combination of a Lift and Throw biotic combo at high levels could easily throw an enemy out of the playable area for an instant-kill. The later games also used this to an extent, though limits on leveling your abilities made it harder.

Western Animation

In The Legend of Korra this is an important mechanic of pro-bending. Forcing an opposing player off the back (and only the back) of the arena and into the surrounding pool removes them from the game for the remainder of the round. Forcing all three opposing players off the back in a single round is an Instant Win Condition, which is why, in a best of three rounds format, the third round is always played. It's the only way left to win for a team down two rounds.

Real Life

Sumo
In Wrestling (Greco-Roman and freestyle), causing an opponent to go out of bounds scores you one point.
Robot Wars
- Ditto the show's video game adaptation.
Gymnastics floor routines deduct points for stepping out of the ring.
In Kendo forcing an opponent of bounds results a foul, which can be a round or match winning point. However, "unfair shoving or pushing" of an opponent out gets the pusher a foul. You're going to have to do it with footwork and clever offense.
- The same is true in Western-style fencing.