Thamihla Kyun Wildlife Sanctuary is a protected area in Myanmar, located on the 0.88 km2 (0.34 sq mi) small uninhabited Diamond Island near the mouth of Pathein River.

[4] Diamond Island is undulating with a coast line of 4.8 km (3.0 mi) consisting of sandy beaches and narrow cliffs running south and west.

Tree species in the island's forest include beach almond (Terminalia catappa), Casuarina equisetifolia, Coconut (Cocos nucifera), silk-cotton tree (Bombax malabaricum), Ficus benghalensis, Lagerstroemia macrocarpa, Xylia dolabriformis, Terminalia belerica and Lannea grandis.

The southern part of the island is open land with bare rocks interspersed with low vegetation.

Birds include brown-headed gull (Chroicocephalus brunnicephalus), black-headed gull (C. ridibundus), white-bellied sea-eagle (Haliaeetus leucogaster), shikra (Accipiter badius), red-whiskered bulbul (Pycnonotus jocosus), white-throated kingfisher (Halcyon smyrnensis), black-hooded oriole (Oriolus xanthornus), Asian koel (Eudynamys scolopaceus), white-breasted waterhen (Amaurornis phoenicurus), common snipe (Gallinago gallinago) and common myna (Acridotheres tristis).