One of the best museums we visited in Paris was the Musee d'Orsay (Museum d'Orsay). This museum is in a beautiful former train station in the heart of Paris along the Seine. The museum itself is a work of art. The museum houses the largest collection of Impressionist art in Europe, featuring artists such as Monet, Manet, Renoir, Degas, Van Gogh and Cezanne. I love Impressionist art. You will also see works from such artists as Gauguin, Seurat and Toulouse-Lautrec. The famous painting Portrait of the Artist's Mother (Whistler's Mother) is also at the d'Orsay but I don't remember seeing it.
Another favorite museum in Paris is the Musee de l'Orangerie which houses Monet's Water Lilies on eight hugh curved panels in four rooms. The water lilies are in the pond at Monet's famous garden in Giverney.