Love Ruins the Realm

""Rulers make bad lovers You better put your kingdom up for sale""

- Fleetwood Mac, "Gold Dust Woman"

A monarch's romantic choices are directly linked to everything going to hell thereafter. Usually, this is for one of three reasons:


 * 1) They're having so much fun with their paramour, they forget about the actual ruling part.
 * 2) It's an extramarital affair or some other sort of slap in the face, and it makes them a lot of enemies. (Common case: it interferes with an Arranged Marriage and disrupts everyone's plans for inheritances, alliances and succession.)
 * 3) Their significant other starts to exert an influence on government policy, and causes problems either deliberately or through simple selfishness.

Rebellious Princesses, however, are completely immune to love-related repercussions. Compare Fisher King.

Anime and Manga

 * In Sailor Moon, particularly in the manga, Serenity and Endymion's love affair resulted in the fall of the Moon Kingdom via Green-Eyed Monster - when Queen Metaria showed up offering power, Beryl jumped at the chance, rallying the people of Earth to follow her in revolt by claiming Endymion's relationship with Serenity meant he was betraying Earth in favor of the Moon Kingdom. When Endymion rejected her, she killed them both.
 * Pretty Guardian Sailor Moon takes it to the extreme, revealing that . This "curse" was carried over to their new incarnations, but they decided to Screw Destiny anyway.
 * Magic Knight Rayearth: anything more would be a giant spoiler. Although
 * Twelve Kingdoms: the empress Jokaku went insane with love for her advisor, Keiki, and slaughtered and exiled all other women from the kingdom. Being that the state of the kingdom is directly dependant on the competency of the ruler in this series, things went downhill very quickly.
 * In Gundam Seed Destiny Yuna Roma Seiran tries to use this trope to convince Cagalli to break off her engagement to Athrun and marry him instead. It nearly works until her brother disagrees

Comic Books

 * One of the Sandman books recounts the story of Dream's love affair with queen Nada. Unfortunately, the heavens didn't approve of a human having an affair with one of the Endless, and started destroying her kingdom's cities left and right until she broke up with him. At which point he sent her to hell, forever.

Fan Fiction

 * The above Sailor Moon example is noted in White Devil of the Moon. Nanoha, who in this fic is the reincarnation of Princess Serenity, calls out Queen Serenity for allowing her daughter to do everything that she did, noting that in addition to the above consequences, the princess was placing herself in danger of coming to harm and sparking an international incident, and potentially allowing Endymion to seize control of the Moon Kingdom through marriage.
 * In Naruto Veangance Revelaitons, Ronan's (albeit twisted) love for Sakura results in . Ronan leaves his kingdom to save her,.

Literature

 * Dido and Aeneas in The Aeneid. According to Virgil, their short fling caused, much later, the Punic Wars. Let this be a lesson to all Good Romans to never put love before duty.
 * Guinevere and Lancelot of the Arthur mythos are another classic example.
 * And though it wasn't exactly love per se - Arthur and his Half-Sister Morguese counts since it produced Mordred.
 * As are Antony and Cleopatra from the Shakespearean play.
 * Which is based on historical records of just how bad this relationship was.
 * Caesar - Cleo's previous paramour was accused of letting his love for the Egyptian Queen cloud his judgement.
 * Even older - bad policy (and subsequent Divine Wrath) in the Old Testament is often blamed on the influence of foreign wives.
 * It wasn't just the foreigners, although they are the most commonly-described - King David's adultery with Bathsheba nearly ruined the rest of his life, although this is attributed in The Bible to God's punishment rather than a natural consequence.
 * It's made explicit with David's son, Solomon. All his famous wisdom didn't do him much good when he started thinking with his other head and taking wives from other kingdoms who swayed his heart away from God, thus setting his kingdom up to fall.
 * of A Song of Ice and Fire. Later, the third book sees ; of course, the realm has already gone to hell by that point, but when the whole fiasco has played out, it's worth a couple of circles. Does not apply with the oft-rumored relationship between Queen Naerys and Aemon the Dragonknight, presumably because Aemon the Dragonknight is an actual heroic figure for a change.
 * Plus fifteen years before Robert Baratheon led a rebellion that ended the Targaryen dynasty after the already married Prince Rhaegar disappeared with Robert's fiancee Lyanna Stark.
 * And ultimately revealed that
 * Ser Barristan finds himself pondering all the various kings and princes who acted on their own feelings and unwittingly brought misery on the realm. He also reveals The Mad King would have rather wed  than his sister Rhaella. The implication being Aery's subsequent madness served to fuel his envy of his childhood friend   to the point of hatred.
 * The nobles (and, perhaps more importantly, his wife) in Christopher Marlowe's play Edward II claim this as their reason for having the king offed: he was spending too much time with his... um... friend Piers Gaveston, a mere commoner.
 * Subverted in Kushiels Legacy. Moirin's relationship with
 * Phaedra's love for Ulfin in The Cup of the World. Made even worse when it's revealed that.

Live Action TV

 * Also shows up in Rome, where Anthony and Cleopatra are having so much fun drinking, screwing, getting high, cross-dressing, etc (yeah, it's that kind of show) that they don't notice till the last minute that Octavian's coming to pwn their asses.
 * Since The Tudors is about Henry VIII, this shows up here when he throws England into political and religious turmoil in order to be with Anne Boleyn.

Video Games

 * This is the reason of why Liu Kang refuses to become Edenia's king, alongside Kitana, in his ending in Mortal Kombat 4.

Western Animation

 * One episode of My Little Pony Friendship Is Magic had the Cutie Mark Crusaders discover their concocted love potion was a poisonous variant, which caused the collapse of a kingdom at some point in the past because of "too enamored to do crap" version of this trope.

Truth in Television

 * Louis XV and Madame la Pompadour were falsely accused of this, for political reasons, to make him look like under the cat's paw. In fact her influence was very limited in foreign politics, she mainly focused on getting various relations cushy jobs. She did strongly influence the kings patronage of various artists, and the Academie Francais to a lesser degree.
 * Lola Montez, the mistress of Ludwig I of Bavaria, has been credited with destroying his popularity and pretty much single-handedly causing a revolution.
 * Ancient Chinese attitudes towards women being what it was, historians very rarely had anything nice to say about wives and concubines of emperors:
 * The last king of the Shang dynasty had a cruel concubine named Daji, who dragged the entire kingdom into senseless debauchery, cruelty and bloodshed.
 * The next dynasty didn't learn the lesson: one late Zhou emperor got his fool ass invaded because he'd keep Crying Wolf to entertain his concubine, so his disgruntled troops refused to mobilize when a real emergency hit.
 * For varying values of "ruin" (there's still no consensus among historians), Empress Wu Ze Tian started out as a concubine, (supposedly) murdered her way up the ladder until she was made head wife, and then forced her own husband and son into early retirement to sit on the throne herself. While this did briefly interrupt the Tang dynasty and result in a Reign of Terror, she also made a lot of significant positive reform.
 * Emperor Xuanzong (reigned 712-756) spent a whole lot of his later reign with his beautiful consort Yang Guifei and passing out all sorts of high offices to her friends and family. Little details like national defense were neglected right up until the inevitable rebellion by a cocky general. The poor consort didn't survive the evacuation, as what troops Xuanzong had left demanded her scapegoat's head.
 * The Dowager Empress Ci Xi of the Qing dynasty was accused of wanting to be the next Wu Ze Tian and at the very least indirectly putting the final nails in the coffin of the Qing dynasty. (She did try to reform, but by then it was too late.)
 * Henrietta Maria the wife of Charles I of England,Scotland and Ireland. Besides being a French Catholic in a Protestant Kingdom she continually advised him to take actions that when discovered led his opponents to regard Charles as untrustworthy and treasonous, such as repeatedly trying to get foreign (and also Catholic) nations to invade in support of Charles in the Civil Wars. TBF she wasn't the only one but Charles was so devoted to his wife he also made catastrophically bad political decisions when he heard rumblings she was threatened, including marching at the head of a troop of soldiers into the English Parliament to arrest his opponents, the event that made War all but inevitable.
 * Henry VIII's attempts to divorce Katherine of Aragon and marry Anne Boleyn led to centuries of religious warfare in England.
 * Ironically, Henry's actions in that case were an attempt to avoid this trope. Apparently, he did love Katherine but didn't think she could give him a son. He believed that his duty to England to provide an heir was more important than his duty to Katherine.
 * And for all that, poor Anne got her head cut off anyway.
 * Because by that point, Henry realized she couldn't give him a son, either, and had already begun courting Jane Seymour—who, as the saying goes, 'had the good fortune to bear a son and the good sense to die immediately afterward.'
 * Procopius (perhaps an Unreliable Narrator) claims that Justinian's marriage to the notorious actress/prostitute Theodora brought about the ruination of the Roman/Byzantine empire.
 * Others opine that Theodora and Justinian were a competent power couple.
 * Judging from her famous quote during a particularly nasty chariot race riot about staying and possibly dying as queen rather then running as beggars, she encouraged her husband to try to quell the riot - one could suggest she was the more competent (or at least the bolder) of the two.
 * One source of Mary, Queen of Scots' unpopularity as a ruler was her alleged tendency to get involved in numerous affairs (granted, her husband was known for being an abusive brute) that undermined her reputation, to the point where she was commonly referred to as a whore (via images of the Mermaid).
 * Antony and Cleopatra, who probably deserve Trope Codifier status even though this is a very Truth-based trope. Interestingly, Antony didn't get in trouble for screwing Cleopatra—such things were rather expected of Roman leaders—but rather for letting her co-rule. Octavian pounced on the opportunity to slander Antony with some nasty PR (he was letting a woman rule!), got the Roman people to back a civil war against an otherwise wildly popular general and the rest is history. Ironically, Cleopatra's actions made political sense; sleeping with Caesar/Anthony kept Egypt independent for several decades after the Romans decided they wanted it.
 * Marie Antoinette, the poor girl, was and still is often accused of influencing her husband inappropriately and substantially.
 * Eric XIV of Sweden (reigned 1560-1568) managed to upset large parts of the Swedish nobility, including his own brothers, during his reign because of his sometimes violent insanity and paranoia. His decision to marry his mistress Karin Månsdotter, the daughter of a common jailkeeper, became the final straw that made it possible for his brothers and other political opponents to dethrone him.
 * For a while, it looked like this was going to happen with Queen Elizabeth I of England (1533-1603) and Robert Dudley. He was universally hated and was generally supposed to have murdered his wife; the Queen's intimate relationship with him scandalized Europe and damaged her reputation. If she had married him, Elizabeth might have had a hard time holding on to her crown. Eventually, she decided to become the "Virgin Queen" and renounce marriage, but she kept her "sweet Robin" close by until he died in 1588.
 * Edward VIII of England was on the verge of causing this. Subverted in that his abdication got rid of a King with fascist sympathies, and put on the throne King George VI, who - with the help of his wife, Lady Elizabeth Bowes-Lyon - listened to Winston Churchill and guided England through World War II. Love Saves The Realm?
 * Although ironically - despite what The King's Speech tells us - Churchill didn't actually want the succession to be diverted. (Just Because, as far as is possible to see - he thought at the time it made a nonsense of the idea of monarchy. And George was also extremely - some might say, as he announced it as king before parliament had agreed on it - inappropriately eager to celebrate the achievements of Neville Chamberlain's peace treaty...)
 * Edward IV married Elizabeth Woodville because of love instead of political reasons. This got him a lot of enemies within his own court, as she was not only completely inappropriate (was the widow of a Lancastrian soldier with two children), but she also did things like securing all the best jobs and marriages for her relatives. This helped cause the Earl of Warwick to fall out with Edward and try to overthrow him, as he felt that Edward wasn't following his advice.