ArtSpan is a San Francisco, California, nonprofit organization that produces the oldest and largest artist open studios event in the United States. Started in 1975, ArtSpan's San Francisco Open Studios (SFOS) takes place over five weekends in October and November each year with a different city district highlighted each weekend. The Open Studios take place in a myriad of different locations within each district. Some are in art galleries, some in apartments, some in garages and some in store fronts. Local publications often make recommendations for each weekend. In 2018, over 800 local artists participated in SFOS.