General François Augustin Regnier de Jarjayes is a high-ranking officer and the head of the royal military who serves as a central figure in the upbringing of his youngest daughter, Oscar. His most defining action is his decision to raise Oscar as a son and a soldier. Desperate for a male heir to carry on the prestigious Jarjayes military legacy after the birth of his sixth daughter, he declares that the child will be raised as a boy. He provides Oscar with a comprehensive military education and rigorous training in swordsmanship from a very young age, with the explicit goal of having her succeed him as the Commander of the Royal Guard at the Palace of Versailles.

In public and private life, General Jarjayes is presented as a strict, proud, and imposing man with an unwavering commitment to the French monarchy. He is a traditionalist who holds deep respect for royal authority and the established social hierarchy of the Ancien Régime. His personality is forged by his military background, making him appear cold, disciplined, and at times harsh. This severity is frequently directed at Oscar, particularly when her actions or personal convictions challenge royal orders or threaten the family's honor. There are instances where his authoritarian nature leads to physical confrontations with his daughter, revealing a temper that conflicts with his disciplined exterior.

His motivations are deeply rooted in family legacy and a rigid sense of duty. While initially, his actions seem driven by a selfish desire for a male successor, his feelings evolve significantly over the course of the story. Beneath his stern facade lies a complex paternal love that becomes more apparent as the narrative progresses. When Oscar leaves the Royal Guard and ultimately sides with the revolutionary cause, General Jarjayes undergoes a profound internal crisis. He comes to recognize the immense emotional burden he placed on his daughter by forcing her to deny her femininity. In a moment of deep remorse, he apologizes to Oscar, tearfully confessing his mistake and expressing regret for the difficult life he imposed on her, believing he has robbed her of the chance to live as a normal woman.

Despite this personal regret, his loyalty to the crown remains steadfast. He struggles to reconcile his love for his revolutionary-minded daughter with his lifelong oath to protect the king. This conflict places him in a tragic position, torn between his duty as a general and his role as a father. In an attempt to protect Oscar from being executed for treason, he even contemplates a mercy killing to spare her from a more brutal death at the hands of the state. His relationships are defined by this tension, particularly with Oscar and her childhood friend turned lover, André Grandier. While initially horrified by the idea of his noble daughter marrying a commoner, he eventually gives André his blessing, acknowledging the sincerity of their love.

General Jarjayes is depicted as a capable military leader with notable strategic skills. His physical and martial prowess is implied through his high rank and his ability to train Oscar in combat. His development is one of gradual disillusionment and sorrow. As the political climate worsens, he watches helplessly as his family is torn apart by forces beyond his control. His wife dies of a broken heart following Oscar's eventual death, a loss he blames himself for, recognizing that his choice to raise her as a soldier led to her demise on the battlefield. After the fall of the monarchy and the execution of the king, he attempts to aid Marie Antoinette in a failed escape plan before ultimately being forced to flee France to avoid execution himself, living out his final years in exile in Italy.