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.

The museum continues to display this very rich collection which features paintings by Giotto, Cima da Conegliano, Luca Signorelli, Francesco Francia, Lorenzo di Credi, Joos van Cleve, Tintoretto, Palma the Younger, Jan Davidsz de Heem, Philippe de Champaigne, Charles Le Brun, Nicolas de Largillière, François Desportes, François Boucher, Rosalba Carriera, Giovanni Paolo Pannini and Jean-Baptiste Greuze; sculptures by Baccio Bandinelli, François Girardon, Jean-Antoine Houdon, Augustin Pajou, Jean-Baptiste Lemoyne and Gois; furniture and decorative art; and a collection of Indian items.