Fire Emblem Gaiden[a] is a tactical role-playing game developed by Intelligent Systems and published by Nintendo for the Famicom.

Set in the same world as its predecessor, Fire Emblem: Shadow Dragon and the Blade of Light, Gaiden follows the battles of two opposing armies on the continent of Valentia, which is torn apart by political strife involving the princess Celica and her childhood friend Alm.

It received mixed reviews from critics, and was later compared to Super Mario Bros.: The Lost Levels and Zelda II: The Adventure of Link as the "black sheep" of the series.

Players assume control of two armies, led by Alm and Celica, who navigate an overworld and can visit towns, where they may recruit new allies or talk to traders to transfer items between the groups.

On easy mode, experience points earned through actions in combat are doubled and items can be exchanged between units beyond vendor stalls.

The players are given a limited number of units, which are each assigned unique character classes that have various functions in battle, such as being mounted or having access to magic.

The two deities, who each held extreme viewpoints on the world, ended up corrupting their subjects, and Zofia was eventually swallowed in a war triggered by its military leader, Chancellor Desaix, who attempted a coup d'état.

It is then explained that Rudolf's invasion was intended to strengthen the continent's military forces and create a champion capable of defeating Duma and Mila, who have both fallen into insanity due to their extreme power.

[6][7] In addition to Kaga, Gunpei Yokoi returned from Shadow Dragon and the Blade of Light as the game's producer, while the visuals were created by Naotaka Ohnishi, Satoshi Machida and Toshitaka Muramatsu.

The system of Shadow Dragon and the Blade of Light was used as the base for various improvements to aspects such as enemy AI, although the gameplay adjustments ended up removing some of the strategic elements.

[21] In a later retrospective article on the Fire Emblem series, Pocket Gamer's Mark Brown compared Gaiden's radical and short-lived shift in gameplay to that of Zelda II: The Adventure of Link.

[4][11] The concept of a navigable overworld map and towns the player could visit was later explored in the Game Boy Advance entry Fire Emblem: The Sacred Stones in 2005.

[13] A full remake of the game, titled Fire Emblem Echoes: Shadows of Valentia, was released worldwide for the Nintendo 3DS in 2017.