Chaalis Abbey was a French Cistercian abbey north of Paris, at Fontaine-Chaalis, near Ermenonville, now in Oise.
It was founded in 1136 by Louis VI of France. There had previously been a Benedictine monastery in the same place. Among the ruins, a chapel with important frescos by Primaticcio survives intact.
The former abbey is now the location of an art museum, the Musée Jacquemart-André. Like the museum of the same name in Paris it houses a part of the former collection of artworks of Nélie Jacquemart-André. At her death in 1912 she gave it to the Institut de France and asked that a museum should be created in Chaalis, where she had spent her childhood.