Hainshallig (also spelled Hayenshallig) was a small Hallig in the North Frisian Wadden Sea, located east of the Hallig of Hooge, that was flooded and sank in 1860.[1] At the time, Hainshallig was leased to a Hooge resident as part of a leasehold estate and was used for the production of hay.[2] A levee may have once led from Hooge to Hainshallig.[3] The area belonged to the Duchy of Schleswig, which was a fiefdom of the Danish crown, now Germany.