Shikanoshima Island (志賀島, Shika-no-shima) is an island in Higashi-ku, Fukuoka, Japan. The island is known as the spot where the Gold Seal of the King of Na, a national treasure, was discovered. The island is about 11 kilometres around and connected to the Umi no Nakamichi (road) on the mainland by a causeway.
On the hill that commands a view of Hakata Bay, two farmers found the golden seal in 1784. The area was developed into a park to commemorate the discovery, and designated Kin-in Park. According to Chinese chronicles, about 2,000 years ago, the Emperor Guangwu of Han, a dynasty of ancient China, granted an envoy from Japan a golden block seal, which was to be presented to the envoy's king. The seal was engraved with the characters 「漢委奴国王」"(Han wa na koku-ō"), meaning "[From the King of] Han, presented to the King of Nakoku". The seal can be seen in the Fukuoka City Museum.
Notable people from the island include Nogizaka46 member Yūki Yoda.