Kotelny Island (Russian: Остров Котельный) and Faddeyevsky Island (О. Фаддеевский) formed as separate islands in the New Siberian Islands group of the eastern Russian Arctic. Over the millennia a sandy accretion, which has been designated as Bunge Land (Бунге Земля), has built up between them forming a single geographical island, one of the 50 largest islands in the world.

The Great Soviet Encyclopedia gives the following areas:

 Kotelny Island 11,665 km² Bunge Land 6,200 km² Faddeyevsky Island 5,300 km² ====== TOTAL 23,165 km² 

Kotelny Island is rocky and hilly, rising to 374 m on Mt. Malakatyn-Tas. Faddeyevsky Island is mainly clay and sand, rising only to 65 m. It is named after a fur trader called Faddeyev who built the first habitation there. Bunge Land is mainly less than 8 m above sea level and is sometimes flooded. It is named after Russian zoologist and explorer A. A. Bunge.