Timonium is a census-designated place in Baltimore County, Maryland, United States. As of the 2020 census, it has a population of 10,458. Prior to 2010 the area was part of the Lutherville-Timonium CDP. The Maryland State Fair is held in Timonium each year near Labor Day on the grounds of the former Timonium Race Course, which is an important site along with Pimlico Race Course in northwest Baltimore and Laurel Park in Prince George's County, along with other former tracks at Bowie and Rosecroft in Maryland thoroughbred horse racing traditions.