Fire Emblem: Seisen no Keifu (ファイアーエムブレム　聖戦の系譜, Faiā Emuburemu Seisen no Keifu, literally Fire Emblem: Genealogy of the Holy War) is a Japanese Super Famicom tactical role-playing game developed by Intelligent Systems and published by Nintendo. It was released on May 14, 1996 in Japan. It is the fourth title in the Fire Emblem series, the second Fire Emblem title for the Super Famicom and was the last game produced by Gunpei Yokoi. The game has received recognition outside Japan through imports and console emulation. It was released on the Japanese Virtual Console service on January 30, 2007, at the price of 900 Wii points.

Seisen no Keifu, like all Fire Emblem games, is a turn-based tactical role-playing game. The player controls a small army of units (characters) as they travel across the land, fighting enemies and liberating castles. For basic gameplay information, see the gameplay basics. There is no limit on how many player units can be deployed; this is balanced by the player receiving fewer controllable units than in other games in the series.

At the start of each chapter, the player holds a castle that must not be conquered by the enemy. In allied castles, units can shop, store items, repair damaged items, and fight in the arena. Each individual unit has its own money; the only units who can give money to others are thieves and units who are in love. Units cannot trade weapons or items. The only way to "give" something to another unit is to sell the item at a pawn shop and have another unit buy it. By visiting repair shops, money can be spent to restore a used weapon before it breaks. In the starting castle, the player can also promote units to a more powerful class when they reach level 20. Rather than being reverted to level 1, the unit will remain at its current level. There are only seven arena opponents to fight for each unit per chapter, as opposed to infinite opponents in other Fire Emblem games. The arena opponents are predetermined for each chapter and are always the same. Units do not die when they have lost an arena battle; instead, they remain alive at 1 hit point.

The majority of gameplay takes place on the battlefield. Seisen no Keifu is the first installment of the Fire Emblem series to implement the weapon triangle, a rock-paper-scissors-like system. In the weapon triangle, swords beat axes, axes beat lances, and lances beat swords. There is also a similar trinity of magic: fire beats wind, wind beats thunder and thunder beats fire. There are also Darkness and Light magic which beat all three of those, and are neutral against each other. Higher character level and statistics can still overcome a weapon triangle disadvantage. Among the features of the battlefield are differing terrains, which give defensive bonuses, gates which can only be opened by triggering a plot event, and villages, which can be attacked and destroyed by bandit enemies. Enemies can only destroy a portion of a village each turn; however, the more the player allows an enemy to tear down a village, the less gold will be rewarded for rescuing it. As opposed to other Fire Emblem games where capturing the enemy's castle ends the chapter, Seisen no Keifu features several enemy castles per chapter, all of which must be captured to proceed.

Seisen no Keifu is the first installment of the series to assign special skills to individual units. Units may also gain skills by belonging to a certain character class. Personal skills may be activated by command on the field, activated automatically under certain conditions, or activated by chance. If units in the first half of the game fall in love, they will pass on their individual skills to their children in the second half. A similar skill system is used in Fire Emblem: Thracia 776, Fire Emblem: Path of Radiance, Fire Emblem: Radiant Dawn and Fire Emblem Awakening.

Seisen no Keifu introduces a romance-based game mechanic to the series. The units in the first half of the game can fall in love after accumulating a certain amount of "Lover points". Units will build Lover points automatically, but they will gain more if the player ends the turn with the units adjacent to one another, and certain pairs have unique conversations at set points in the game, which give a large amount of Lover points. If two units are paired, and the mother survives the first half, the two parents will pass their weapons and personal skills on to their children, who are the majority of playable units in the second half. Weapons will only be inherited if the child can use it in their first class, unless it is a Holy Weapon, which is always inherited. The parents also pass on their Holy Blood and their stat growths, giving the player some manner of control over their units' growth rates. If some of the female player units in the first half die or do not fall in love, substitute player units appear in their children's place. The children can also fall in love, though this does not produce a "third generation". Units in love in either generation may activate random critical hits when they stand next to their lover.