Gilles de Rais was born around c. 1405, into the most distinguished noble families of western France—namely the Houses of Retz, Laval, and Craon—inheritances that granted him vast estates in Brittany, Anjou, Poitou, Maine, and Angoumois. Following the death of his parents, he was raised by his maternal grandfather, Jean de Craon, who later guided his education and early career.

He first entered the royal sphere in 1425 during the diplomatic events in Saumur, where he aligned with King Charles VII, and benefitted from his support when the king intervened to restore some of Gilles's Breton lands with the help of Arthur de Richemont. Around this time, he also received mentorship from Guillaume de la Jumellière, a senior advisor of Yolande of Aragon, in order to launch his military career.

From 1427 onward, Gilles emerged as a seasoned guerrilla commander, conducting aggressive raids alongside Ambroise de Loré and Jacques de Dinan along the borders of Maine. He participated in several operations—capturing Ramefort and Malicorne and striking at English-held Château du Lude, gaining control of territories and sometimes executing captured English-aligned individuals perceived as traitors.

In 1428, he financed the ransom of his cousin André de Lohéac, demonstrating both generosity and family loyalty. When Joan of Arc emerged, Gilles became one of her closest allies—present at Chinon in February 1429 and later serving as her escort during the relief of Orléans. He commanded troops during key battles such as Jargeau and Patay, led the vanguard toward Reims for Charles VII’s coronation, and was elevated to Marshal of France on 17 July 1429, a rare honor he shared with Joan herself.

However, Gilles’s fortunes soon turned. His lavish spending on entertainments, troops, and cultural patronage drained his wealth, leading to mounting financial strain. His family—particularly his brother René de La Suze and the powerful House of Laval—accused him of mismanagement, compelling the king to place him under interdict in July 1435.

By the mid-1430s, Gilles de Rais had fallen from royal favor—and increasingly retreated from the public stage. Stripped of prestige and beset by financial ruin, he withdrew from military life to pursue secretive interests. Around 1438–1439, he became entangled with occult practices, notably through two of his servants: the priest Eustache Blanchet and the Tuscan cleric and alchemist François Prelati. According to their trial testimonies, Gilles dispatched Blanchet to seek out practitioners of alchemy—a quest that led Blanchet to recruit Prelati in Florence. In these sessions, Prelati claimed to have attempted to summon a demon named “Barron” at the Tiffauges Castle under Gilles's direction. When Barron failed to appear after three attempts, Prelati alleged that the demon demanded a child offering. Gilles responded by providing human remains in a glass vessel during a subsequent ritual, but the invocation again failed—leaving both men bitter and financially depleted by their occult pursuits.

These dark preoccupations coincided with the onset of Gilles’s most horrific crimes. In his own confession, rendered during his trial in October 1440, Gilles admitted that his first assaults on children occurred between spring 1432 and spring 1433—though the exact dates remain unknown. Over the following years, local rumors multiplied; villagers came forward complaining that children who had entered Gilles’s castle seeking food were never seen again.

Gilles’s slide into outright confrontation with authority came to a head in May 1440, when he staged a violent act of force at Saint‑Étienne‑de‑Mer‑Morte. After reclaiming its castellany—initially granted to his brother René—he found that the Duke of Brittany’s treasurer had placed it under the control of his tonsured brother, Jean Le Ferron. In revenge, on Pentecost (15 or 16 May), Gilles ambushed a group of fifty to sixty men, burst into the parish church brandishing a weapon, and threatened to kill Le Ferron if he did not renounce the stronghold. The cleric yielded, opening the gates to Gilles’s men, after which Gilles arrested Le Ferron and other ducal officials—including Jean Rousseau, the sergeant-general of Brittany. 

The response from ecclesiastical and secular authorities was swift. Bishop Jean de Malestroit of Nantes initiated a formal inquisitio infamiae, an investigation into Gilles's public reputation, particularly rumors of child murder and demonic pacts. On 29 July 1440, Malestroit issued letters patent accusing Gilles of raping and murdering numerous children, invoking demons, and engaging in heresy. Simultaneously, secular authorities gathered testimony under Judge Pierre de L'Hôpital’s direction, aiming to build a comprehensive legal case.

By 24 August, Duke John V had secured assistance from his brother, Constable Arthur de Richemont, who seized Tiffauges and freed Le Ferron. Two weeks later, on 15 September 1440, Gilles de Rais was arrested at Machecoul Castle. His accomplices—including Prelati, Blanchet, the servants Henriet Griart and Étienne Corillaut (“Poitou”), and the women Tiphaine Branchu and Perrine Martin (“la Meffraye”) accused of providing children—were also apprehended, though others had already fled. Gilles was quickly transferred to the Château des ducs de Bretagne in Nantes.

During the dual ecclesiastical and secular trials, Gilles confessed on 21 October 1440, ending any need for torture to extract statements. Witness testimony—including grieving parents—painted a chilling picture of child disappearances around his properties. On 23 October, his servants Poitou and Henriet were condemned to death. Gilles himself received his sentence on 25 October: the ecclesiastical court determined he had murdered "one hundred and forty children, or more," while the secular court cited "several small children." He was permitted to make a final confession and was granted a request to be buried at the Carmelite monastery in Nantes.

The sentence was carried out on 26 October 1440: Gilles de Rais was hanged and then burned. Noblewomen reclaimed his body to ensure church burial. His accomplices were executed in the same manner, but their remains were burned entirely, the ashes scattered.