The parish, dedicated to Saint Germain, dates back to Merovingian times. Emma, daughter of Leutgarde and Thibaut-le-tricheur, having married William Ironarm, Count of Poitiers, founded the Abbey of Bourgueil, which she endowed with her Normandy possessions, inherited from her mother, widow of William Longsword. Coudres and Marcilly-la-campagne were included in this endowment.
The two Marcillys had the same lords for a long time.
Around 1060, Teudon, Lord of Marcilly, approved the gift of the land of Les Loges to the Abbey of Saint Père de Chartres by Robert des Loges.
In 1107, Foulques de Marcilly, the second of the name, founded the Abbey of Breuil Benoit (near Marcilly-sur-Eure). By the Treaty made in 1194 between Philip Augustus and Richard the Lionheart, Marcilly was part of the King of France's estates, on the border with Normandy. We were ROYAL!
In 1226, Fulk IV, Lord of Marcilly, gave the Monks of Saint Taurin an annuity on his mills in Marcilly.
During the 15th-century invasion, the King of England granted Jean Yprès on August 27, 1419, all the lands that belonged to Fulk of Marcilly, "in default," that is, devoted to France.
The coat of arms of the House of Marcilly was a chevron, but the color, as well as that of the background of the shield, are unknown.
At the 1470 watch, Jehan Tailleman, Lord of Marcilly-la-campagne, appeared naked. Aged 90, he could not wear a harness, and his fiefdom was very small. It is discharged, on condition of providing a vougier. (13th century weapon, made of a sharp and asymmetrical blade fixed to the end of a handle)