Guy de Dammartin, also written Gui, Guiot, Guyot or Guillot and Dampmartin, (* 13401345; 1398) was a French architect and sculptor of the Middle Ages. He built the ducal palaces of Poitiers and Bourges and founded the style of the late Gothic French Flamboyant around 1380.
It is believed that Guy de Dammartin was the brother of Drouet de Dammartin, architect Philip the Bold. He worked under the direction of his teacher, the royal Parisian architect Raymond du Temple, at the same time as his brother in the Louvre. From 1362 to 1365 he worked there as a sculptor and, in the course of the embellishment ordered by King Charles V, together with Jacques de Chartres, created the statues of the Dukes of Berry and Burgundy for the famous spiral staircase grande vis. During this time, he worked on the decor of the ceiling together with Jean de Saint-Romain.
Shortly before 1370, Guy de Dammartin joined the services of Duke Jean de Valois as construction manager. Dammartin was in charge of all the Duke's construction projects. In 1367, he began the transformation of Mehun-sur-Yèvre Castle, and in 1374 he restored Lusignan Castle. Between 1380 and 1389, he redesigned the castle in Riom and built the Sainte-Chapelle there. From 1382 to 1388, he renovated the ducal palace in Bourges, including the Sainte-Chapelle.
The artist's genius manifested itself in the French style of the flamboyant he created, which he shaped in arches, ceilings and windows. At the end of the 1380s, in Poitiers, he restored the early Gothic palace of the former Dukes of Aquitaine (now the Palace of Justice). The showpiece is the multi-level chimney wall, which closes the narrow side of the large hall like a theatre backdrop and whose upper part is occupied by tracery windows and eyelashes. Within the secular architecture, it is regarded as an excellent example of the Flamboyant style that was to dominate France for more than a century.