In FGO, Ruler is an Extra Class Servant, summoned under unusual circumstances. They govern Holy Grail Wars and are directly summoned by the grail in potentially threatening situations. They possess administrative rights and Command Spells.

In the Fate series, the Ruler class, summoned by the Holy Grail to oversee the Grail Wars, has a base death rate of 35%. The game features 17 playable Ruler characters, each with distinct abilities.

Jeanne d'Arc (ジャンヌ・ダルクWP, Jan'nu Daruku?), Class Name Ruler (ルーラー, Rūrā?), is the Ruler-class Servant in the Great Holy Grail War of Fate/Apocrypha. She is one of the Servants of Ritsuka Fujimaru of the Grand Order conflicts of Fate/Grand Order.

裁定者（ルーラー，Ruler），出自《Fate/Apocrypha》，书中主要指圣女 贞德 的职阶，以及人物名称的代名词。 是 圣杯 为被召唤的 从者 （サーヴァント，Servant）所准备的“容器”，即“ 职阶 （クラス，Class）”之一。 Ruler被召唤的情况大约分为两种：其一为该次 圣杯战争 的形式非常特殊，结果为未知数，也就是圣杯判断出需要Ruler的情况；其二为圣杯战争的影响有可能令世 …

Amakusa Shirou TokisadaWP (天草 四郎 時貞WP, Amakusa Shirō Tokisada?), Class Name Ruler (ルーラー, Rūrā?) is the Ruler-class Servant of the Einzbern Master in the Third Holy Grail War in the world of Fate/Apocrypha.

Ruler (ルーラー, Rūrā?), the Standard-Bearer who Correctly Guides the Holy Grail War (聖杯戦争を正しく導く旗手, Seihai Sensō wo Tadashiku Michibiku Kishu?), is the Ruler-class Servant in the Great Holy Grail War of Fate/Apocrypha.

Rulers are typically powerful and selfless individuals who have no desire for the Holy Grail and possess the ability to be impartial: thus, most Rulers are Saints or were very close to sainthood in life. Any Ruler summoned by the FATE summoning system must meet the qualifications for this role, even if a Holy Grail War is not taking place.

2018年2月2日 · Ruler was summoned because Shirou did exactly that. The guy that should be doing his job as an overseer decided to gather 7 more Servants for his own thing.

—Standard-Bearer who Correctly Guides the Holy Grail War. Virtuous warriors summoned by the Holy Grail itself, tasked with governing the rituals of the Grail Wars.— Rulers have a base damage...

Uesugi Kenshin (上杉謙信?), Class Name Ruler (ルーラー, Rūrā?), is a Ruler-class Servant summoned by Ritsuka Fujimaru in the Grand Orders of Fate/Grand Order. The War God of Echigo, Uesugi Kenshin who was known as a righteous warlord in an age of wars.