Londontowne is an unincorporated area and former census-designated place (CDP) in Anne Arundel County, Maryland, United States, and the site of a former colonial seaport founded on the South River in 1683.

London Town was a colonial seaport settlement founded in 1683 near Annapolis.

It was once considered as the site for the Province of Maryland and was for a time as prominent in trade as Annapolis and Williamsburg, Virginia.

It declined and disappeared by the 19th century for reasons including its non-selection as a tobacco inspection station, economic depression, and the Revolutionary War.

Speculation exists that the South River Club's first clubhouse was built here.

The park includes the London Town Publik House, listed on the National Register of Historic Places and designated a National Historic Landmark, as well as reconstructed period buildings, a public museum, an archaeology lab, and extensive gardens.