Timbun Mata Island (or Pulau Timbun Mata) is the largest island on the south side of Darvel Bay, in Semporna, Sabah, Malaysia. It is over 26 kilometres long and at the widest is almost 10 kilometres wide. The island is mountainous and was formerly (pre-2000) densely wooded. Mt. Tannabalu, the highest point at 620 m., is a conical, extinct volcano located at the center of the island. A secondary peak, Mt. Sedungal, at the east end of the island rises to 489 m. The south side of the island is only separated from the mainland by a shallow channel known as the Trusan Sigalong.