Chrysaster ostensackenella is a moth of the family Gracillariidae. It is known from Canada (Québec and Nova Scotia) and the United States (Illinois, Kentucky, New York, Maine, Maryland, Michigan, Vermont, Arizona, Massachusetts, North Carolina and Connecticut).
The larvae feed on Robinia species, including Robinia hispida, Robinia neomexicana, Robinia pseudacacia and Robinia viscosa. They mine the leaves of their host plant. The mine has the form of a yellowish blotch mine. The mine usually occurs on the upperside, but occasionally on the underside, of the leaflet. It is nearly circular in its early stages, but later in development, it becomes irregular in shape.