Louis XVI, referred to as Luigi XVI in some localized versions of the anime Lady Oscar, is the Dauphin of France who becomes king after the death of his grandfather Louis XV. He is a historical figure adapted into the story and serves as a supporting character within the narrative of the French court and the unfolding revolution.

In terms of background, Louis is the grandson of King Louis XV and is married to the Austrian archduchess Marie Antoinette in a political alliance meant to strengthen ties between France and Austria. He ascends the throne at a young age, inheriting a kingdom already burdened by financial troubles and growing social unrest. He is depicted as a man who would have preferred a quiet life away from the burdens of rule, often finding solace in hobbies such as lock-making and hunting rather than the demands of governance.

His personality is defined by a gentle, mild, and timid nature. He is shy and easily rattled, lacking the assertive confidence expected of a monarch. Louis is shown to be deeply devoted to his wife, Marie Antoinette, and his affection for her sometimes prevents him from taking the firm political actions that might have addressed France's mounting crises. He is often indecisive and reluctant to impose his will, which leaves him vulnerable to the influence of courtiers and his own insecurities. Despite his weak-willed exterior, he is not malicious; he genuinely wishes to be a good husband and king but lacks the strength to navigate the treacherous politics of Versailles or the revolutionary fervor rising outside its gates.

His primary motivation is his love for Marie Antoinette and his desire to protect his family. He also struggles with a sense of duty to his crown and his country, but his inability to make difficult decisions or assert authority leads to paralysis in the face of national crisis. He is motivated by a desire for stability and peace, yet he is overwhelmed by the forces of history that he cannot control.

Louis's role in the story is that of a tragic monarch whose reign is overtaken by the French Revolution. He is a supporting figure whose presence highlights the decadence and fragility of the old regime. He interacts most closely with Marie Antoinette, serving as her husband and king, though their relationship is strained at times by his social awkwardness and her own loneliness. He also has a professional relationship with Oscar François de Jarjayes, the captain of the Royal Guard, whom he respects as a loyal protector of the crown. His interactions with other nobles and revolutionaries underscore his inability to hold together a collapsing system.

His character development is subtle but meaningful. He begins as a hesitant and somewhat passive heir, unsure of his role. As he becomes king, he struggles to assert himself but remains largely ineffective. As the revolution intensifies, he is forced to confront his own limitations. He is captured, imprisoned, and eventually put on trial. In his final moments, he faces his execution with a quiet dignity, focusing on his family until the end. His arc is one of a well-meaning but inadequate ruler who is swept away by events he could neither prevent nor guide.

Louis does not possess notable physical abilities or combat skills relevant to the story. He is not a warrior or a strategist. His significance lies in his position as king and the symbolic weight of his failure to lead effectively during a time of profound change. His weakness contrasts sharply with the strength and resolve of characters like Oscar, and his tragic fate serves as a key element of the story's historical and emotional landscape.