The Peace of Saint-Germain-en-Laye was signed on 8 August 1570 by Charles IX of France, Gaspard II de Coligny and Jeanne d'Albret, to end the third war (1568-70) of the French Wars of Religion.

The Peace went much further than the March 1568 Peace of Longjumeau by establishing specific rights and responsibilities for French Protestants, generally known as Huguenots. Freedom of worship was permitted in two towns per gouvernment, while the Huguenots were allowed to maintain armed garrisons in four towns for a period of two years, after which they had to be returned to Royal control. However, the civil war resumed in 1572 after the targeted assassination of Huguenot leaders assembled in Paris spiralled into the St. Bartholomew's Day massacre.

Following the outbreak of civil war in 1568, the Huguenots under Coligny and Condé opted to defend the south-west by fortifying towns such as Angoulême and Cognac. As they moved south in March 1569, their rear guard was trapped by the Royalists at Jarnac, with Condé cut down after surrendering. However, the bulk of the Huguenot army reached Cognac, with Coligny assuming leadership on behalf of Henry of Navarre and Condé's son Henri.

At Châlus on 11 June, Coligny joined up with 14,000 German mercenaries financed by Elizabeth I of England, originally led by the Duke of Zweibrücken who died shortly before their meeting. This combined army of 25,000 defeated a slightly larger royalist force at La Roche-l'Abeille on 25th. They then laid siege to Poitiers, which was held by Henry I, Duke of Guise; it was still resisting when the main Royal army under Tavannes invested the nearby Huguenot town of Châtellerault.

Forced to withdraw from Poitiers, on 3 October Coligny's forces were decisively defeated at the Battle of Moncontour, but although his army incurred heavy casualties, the remnants were able to retreat in good order. Rather than pursuing Coligny, Tavannes moved onto Saint-Jean-d'Angély, whose possession would enable him to break the Huguenot hold on Aquitaine. Although the town surrendered on 2 December, the Royalists lost thousands of men to disease or hunger, while many of their Swiss and German mercenaries mutinied after not being paid.

Coligny and his remaining troops had moved into Languedoc, where he linked up with 4,000 men led by Montgomery. After an unsuccessful siege of Toulouse in January 1570, their combined force marched north through the Rhone valley towards Paris and reached Montbrison in May. Learning that a Royalist force under Brissac was advancing on the nearby Huguenot stronghold of La Charité, Coligny intercepted and defeated him at Arnay le Duc on 25 June 1570. With Paris under threat, the state bankrupt and the Royal army in ruins, this gave him a strong position to negotiate with Charles IX of France.

No sooner had the war begun than moderate Politique voices on the royal council advocated for a return to status quo ante bellum. The bishop Jean de Monluc as early as 2 December 1568 argued for a restoration of the edict of Longjumeau, and the provision of a governorship to Condé, Armand de Gontaut, baron de Biron likewise refused to serve in a war he felt was unjust. Hôpital too advocated for such a settlement, however he had been marginalised from the government by the beginning of the war, and had lost his seals to the chancellorship. The financial difficulties that had forced the crown to conclude the peace of Longjumeau the prior year also played upon the king, who considered in January the possibility of a temporary truce until proper funding for the armies and mercenaries could be arranged.

When the battle of Jarnac was not followed by a disintegration of the Protestant army, as expected, the crown's army itself began to fall apart in the summer, mutinous for lack of pay and suffering from disease. This motivated more serious outreaches of peace, and Catherine broached the idea of a marriage between Margaret of Valois-Angoulême and Henry IV of France to seal away the civil war, whilst the Huguenot army was encamped outside of Poitiers. Coligny was likewise interested in peace at this time, and advocated for full freedom of religion, and the declaration of a war against Spain to take advantage of the situation in the Netherlands. The king rebuffed these attempts, offering amnesty to the leadership if they laid down their arms.