苏门答腊（印尼语：Sumatera）是印尼最西面的一个大岛，也是全球第六大岛屿。全岛面积达47万平方公里。

苏门答腊岛呈西北—东南走向，在中间与赤道相交叉，由两个地区组成：西部巴里散山脉（Barisan Mountains）和东部的沼泽地。

苏门答腊岛东南与爪哇岛隔着巽他海峡相望，北方隔着马六甲海峡与马来半岛遥遥相对，东方隔着卡里马达海峡（Karimata）毗邻婆罗洲，西方濒临印度洋。

巴里散山脉为青藏高原新生代山脉的连续，纵贯苏门答腊岛。该地区发现了煤、黄金矿床。火山所喷发的矿物质使得土壤肥沃。山脉景象优美而迷人，如多巴湖（Lake Toba）周围区域。

Sumatra (Indonesian:Sumatera) is an island in western Indonesia and part of the Sunda Islands. It is the largest island that is entirely in Indonesia (two larger islands, Borneo and New Guinea, are shared between Indonesia and other countries) and the sixth largest island in the world at 473,481 km (including adjacent islands such as the Riau Islands and Bangka Belitung Islands).