印度(du)洋(yang)在古(gu)代稱為(wei)(wei)“厄立特(te)里(li)亞海”，早見于古(gu)希(xi)臘(la)(la)地理學家希(xi)羅多德（前(qian)484-前(qian)425年）所(suo)著(zhu)《歷史》一書及其(qi)編(bian)繪的(de)世(shi)界地圖中。“厄里(li)特(te)里(li)亞”（ERYTHREA）希(xi)臘(la)(la)文(wen)原意(yi)為(wei)(wei)紅色，全(quan)名意(yi)為(wei)(wei)紅海。
“印度洋”這(zhe)一名(ming)稱(cheng)相對出(chu)現(xian)得較晚(wan)。公(gong)(gong)元1世(shi)紀(ji)(ji)后(hou)期(qi)的(de)羅(luo)馬地理(li)學家彭(peng)波(bo)尼烏(wu)斯·梅拉(la)可能(neng)是早使(shi)用(yong)此名(ming)的(de)人。公(gong)(gong)元10世(shi)紀(ji)(ji)，阿拉(la)伯人伊本·豪卡勒編(bian)繪(hui)的(de)世(shi)界地圖上也使(shi)用(yong)了這(zhe)個名(ming)字。
近(jin)代正式使用印度洋(yang)一(yi)名(ming)則是在(zai)1515年左右，當(dang)時(shi)中歐(ou)地圖學家舍納爾編繪的地圖上(shang)，把這片(pian)大(da)洋(yang)標注為“東方的印度洋(yang)”，此處(chu)的“東方”一(yi)詞是與大(da)西洋(yang)相對而(er)言的。
1497年，葡萄牙(ya)航(hang)海家達·伽馬東航(hang)尋(xun)找(zhao)印(yin)度，便將(jiang)沿途所經過的洋面統稱之為(wei)印(yin)度洋。
1570年奧爾太利(li)烏斯編繪(hui)的(de)(de)世界(jie)地圖集中，把“東方的(de)(de)印度(du)洋(yang)”一(yi)名(ming)去掉“東方的(de)(de)”，簡化為“印度(du)洋(yang)”。這(zhe)個名(ming)字逐漸(jian)被人們(men)接(jie)受，成為通用的(de)(de)稱呼(hu)。
印度(du)(du)洋(yang)(yang)(yang)是聯系(xi)亞洲(zhou)、非(fei)洲(zhou)和(he)大(da)洋(yang)(yang)(yang)洲(zhou)之(zhi)間的交通要道。從印度(du)(du)洋(yang)(yang)(yang)往西(xi)北通過曼德海(hai)(hai)峽(xia)(xia)、紅海(hai)(hai)；蘇伊士運河、地(di)中海(hai)(hai)和(he)直布(bu)羅陀(tuo)海(hai)(hai)峽(xia)(xia)到(dao)達西(xi)歐；向(xiang)西(xi)南經好望角進入大(da)西(xi)洋(yang)(yang)(yang)，通向(xiang)歐美沿(yan)(yan)海(hai)(hai)各地(di)；向(xiang)東北經馬(ma)六甲海(hai)(hai)峽(xia)(xia)和(he)龍目海(hai)(hai)峽(xia)(xia)進入太平洋(yang)(yang)(yang)。印度(du)(du)洋(yang)(yang)(yang)沿(yan)(yan)岸(an)是世(shi)界資源的一(yi)個重要出口(kou)地(di)，沿(yan)(yan)岸(an)各國出口(kou)的石油、礦砂、橡膠(jiao)、棉(mian)花、糧食和(he)進口(kou)的水泥、機械產品(pin)和(he)化工產品(pin)等(deng)大(da)宗貨物都需要依靠廉價的海(hai)(hai)洋(yang)(yang)(yang)運輸，再加上大(da)量(liang)(liang)的過境運輸，使印度(du)(du)洋(yang)(yang)(yang)有較大(da)的運輸量(liang)(liang)，擁(yong)有世(shi)界l/6的貨物吞吐量(liang)(liang)和(he)近1/10的貨物周轉量(liang)(liang)。
印(yin)度洋(yang)(yang)的(de)(de)航(hang)運(yun)業(ye)雖不(bu)如大(da)西(xi)洋(yang)(yang)和太平洋(yang)(yang)發達(da)，但由于中東地(di)(di)區(qu)盛產的(de)(de)石(shi)油(you)通過印(yin)度洋(yang)(yang)航(hang)線(xian)(xian)(xian)源源不(bu)斷(duan)向外(wai)輸(shu)(shu)出(chu)(chu)，因而(er)印(yin)度洋(yang)(yang)航(hang)線(xian)(xian)(xian)在世界(jie)(jie)上(shang)(shang)占有(you)重(zhong)要(yao)(yao)的(de)(de)地(di)(di)位。印(yin)度洋(yang)(yang)上(shang)(shang)運(yun)輸(shu)(shu)石(shi)油(you)的(de)(de)航(hang)線(xian)(xian)(xian)有(you)兩條：一(yi)條是出(chu)(chu)波斯灣向西(xi)，繞過南非的(de)(de)好望角或(huo)者通過紅海(hai)(hai)(hai)、蘇伊(yi)士運(yun)河，到(dao)歐洲和美國。這是世界(jie)(jie)上(shang)(shang)重(zhong)要(yao)(yao)的(de)(de)石(shi)油(you)運(yun)輸(shu)(shu)線(xian)(xian)(xian)。一(yi)條是出(chu)(chu)波斯灣向東，穿過馬(ma)六(liu)甲海(hai)(hai)(hai)峽或(huo)龍(long)目海(hai)(hai)(hai)峽到(dao)日本(ben)和東亞其他國家。霍爾木茲海(hai)(hai)(hai)峽在印(yin)度洋(yang)(yang)航(hang)線(xian)(xian)(xian)上(shang)(shang)占有(you)重(zhong)要(yao)(yao)地(di)(di)位，波斯灣地(di)(di)區(qu)出(chu)(chu)口石(shi)油(you)總量90%從此海(hai)(hai)(hai)峽運(yun)出(chu)(chu)，因而(er)霍爾木茲海(hai)(hai)(hai)峽被稱為(wei)“石(shi)油(you)海(hai)(hai)(hai)峽”。蘇伊(yi)士運(yun)河經馬(ma)六(liu)甲海(hai)(hai)(hai)峽的(de)(de)航(hang)線(xian)(xian)(xian)，是印(yin)度洋(yang)(yang)東西(xi)間一(yi)條重(zhong)要(yao)(yao)的(de)(de)航(hang)道，運(yun)輸(shu)(shu)量巨大(da)，它將西(xi)歐、地(di)(di)中海(hai)(hai)(hai)沿(yan)岸各國的(de)(de)經濟與遠東及(ji)北美洲西(xi)海(hai)(hai)(hai)岸各國的(de)(de)經濟緊(jin)密地(di)(di)聯系(xi)起(qi)來。
印(yin)度洋(yang)的地(di)理(li)位置非(fei)常(chang)重(zhong)要(yao)，是(shi)溝通(tong)(tong)亞洲(zhou)(zhou)(zhou)、非(fei)洲(zhou)(zhou)(zhou)、歐洲(zhou)(zhou)(zhou)和(he)大洋(yang)洲(zhou)(zhou)(zhou)的交通(tong)(tong)要(yao)道。向(xiang)東(dong)(dong)通(tong)(tong)過(guo)馬(ma)(ma)六(liu)甲海峽可以進(jin)入太平洋(yang)，向(xiang)西繞過(guo)好望(wang)角(jiao)可達大西洋(yang)，向(xiang)西北通(tong)(tong)過(guo)紅海、蘇伊士(shi)運河，可入地(di)中海。航線主(zhu)要(yao)由亞、歐航線和(he)南亞、東(dong)(dong)南亞、南非(fei)、大洋(yang)洲(zhou)(zhou)(zhou)之間的航線。印(yin)度洋(yang)的海底電(dian)纜多分布在北部，重(zhong)要(yao)的線路有亞丁—孟買—馬(ma)(ma)德拉斯(si)—新加坡(po)線；亞丁—科(ke)(ke)倫坡(po)線；東(dong)(dong)非(fei)沿(yan)岸(an)線。塞(sai)舌爾群(qun)島的馬(ma)(ma)埃島、毛里求斯(si)島和(he)科(ke)(ke)科(ke)(ke)斯(si)群(qun)島是(shi)主(zhu)要(yao)的海底電(dian)纜樞紐站(zhan)。沿(yan)岸(an)港(gang)口終年不凍，四季通(tong)(tong)航。
印度洋(yang)西南以通過南非厄加勒斯特的(de)經(jing)線(xian)同(tong)大(da)西洋(yang)分界(jie)，東(dong)南以通過塔斯馬尼(ni)亞(ya)島東(dong)南角至南極大(da)陸的(de)經(jing)線(xian)與太平洋(yang)聯結。印度洋(yang)的(de)輪(lun)廓為北部為陸地封閉，南面則以南緯60°為界(jie)，與南冰(bing)洋(yang)相(xiang)連。
印度(du)洋(yang)的主要屬海(hai)(hai)和海(hai)(hai)灣(wan)(wan)是紅海(hai)(hai)、阿拉伯(bo)海(hai)(hai)、亞丁灣(wan)(wan)、波斯灣(wan)(wan)、阿曼灣(wan)(wan)、孟加拉灣(wan)(wan)、安(an)達曼海(hai)(hai)、阿拉弗拉海(hai)(hai)、帝汶海(hai)(hai)、卡奔塔利(li)亞灣(wan)(wan)、大(da)澳大(da)利(li)亞灣(wan)(wan)、莫桑比(bi)克海(hai)(hai)峽等等。
印度洋有很多島(dao)(dao)(dao)(dao)嶼，其中(zhong)大部(bu)分(fen)是大陸島(dao)(dao)(dao)(dao)，如馬達加(jia)斯(si)加(jia)島(dao)(dao)(dao)(dao)、斯(si)里蘭卡島(dao)(dao)(dao)(dao)、安達曼群(qun)(qun)(qun)島(dao)(dao)(dao)(dao)、尼科巴群(qun)(qun)(qun)島(dao)(dao)(dao)(dao)、明(ming)打(da)威群(qun)(qun)(qun)島(dao)(dao)(dao)(dao)等。留尼汪島(dao)(dao)(dao)(dao)、科摩羅群(qun)(qun)(qun)島(dao)(dao)(dao)(dao)、阿姆(mu)斯(si)特丹島(dao)(dao)(dao)(dao)、克(ke)羅澤群(qun)(qun)(qun)島(dao)(dao)(dao)(dao)、凱(kai)爾(er)蓋朗群(qun)(qun)(qun)島(dao)(dao)(dao)(dao)為火(huo)山島(dao)(dao)(dao)(dao)。拉克(ke)沙(sha)群(qun)(qun)(qun)島(dao)(dao)(dao)(dao)、馬爾(er)代夫群(qun)(qun)(qun)島(dao)(dao)(dao)(dao)、查戈(ge)斯(si)群(qun)(qun)(qun)島(dao)(dao)(dao)(dao)，以及爪哇西(xi)南的圣誕島(dao)(dao)(dao)(dao)、科科斯(si)群(qun)(qun)(qun)島(dao)(dao)(dao)(dao)都是珊(shan)瑚島(dao)(dao)(dao)(dao)，馬達加(jia)斯(si)加(jia)島(dao)(dao)(dao)(dao)是南回歸線(xian)穿過的島(dao)(dao)(dao)(dao)。
印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)底(di)(di)地貌錯(cuo)綜復雜，除洋(yang)(yang)(yang)(yang)(yang)底(di)(di)中(zhong)(zhong)(zhong)(zhong)(zhong)(zhong)部(bu)有(you)呈(cheng)“入”字形(xing)的(de)(de)大(da)(da)洋(yang)(yang)(yang)(yang)(yang)中(zhong)(zhong)(zhong)(zhong)(zhong)(zhong)脊外，東(dong)(dong)(dong)(dong)(dong)部(bu)尚有(you)東(dong)(dong)(dong)(dong)(dong)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)和島(dao)弧、海(hai)(hai)(hai)(hai)(hai)(hai)(hai)溝帶(dai)，在海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)、海(hai)(hai)(hai)(hai)(hai)(hai)(hai)丘、海(hai)(hai)(hai)(hai)(hai)(hai)(hai)臺之(zhi)間分(fen)布著許多海(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆。印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)的(de)(de)大(da)(da)洋(yang)(yang)(yang)(yang)(yang)中(zhong)(zhong)(zhong)(zhong)(zhong)(zhong)脊，包(bao)括中(zhong)(zhong)(zhong)(zhong)(zhong)(zhong)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)、阿拉(la)伯一(yi)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)、西(xi)南(nan)(nan)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)和東(dong)(dong)(dong)(dong)(dong)南(nan)(nan)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)。中(zhong)(zhong)(zhong)(zhong)(zhong)(zhong)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)°嶺(ling)(ling)(ling)(ling)(ling)(ling)從(cong)阿姆斯特(te)丹島(dao)向(xiang)(xiang)(xiang)北(bei)延(yan)伸(shen)，一(yi)般高(gao)于(yu)(yu)兩側(ce)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆1300-2500米(mi)，平均寬(kuan)度(du)(du)(du)(du)(du)(du)達800千米(mi)左右，由(you)于(yu)(yu)被一(yi)些(xie)與之(zhi)垂(chui)直(zhi)或斜(xie)交(jiao)的(de)(de)斷(duan)(duan)(duan)裂帶(dai)切斷(duan)(duan)(duan)錯(cuo)開(kai)，中(zhong)(zhong)(zhong)(zhong)(zhong)(zhong)脊裂谷表現時斷(duan)(duan)(duan)時續的(de)(de)特(te)征，因此中(zhong)(zhong)(zhong)(zhong)(zhong)(zhong)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)形(xing)態崎嶇(qu)破碎(sui)。中(zhong)(zhong)(zhong)(zhong)(zhong)(zhong)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)向(xiang)(xiang)(xiang)西(xi)北(bei)延(yan)伸(shen)形(xing)成(cheng)阿拉(la)伯一(yi)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)，高(gao)度(du)(du)(du)(du)(du)(du)較大(da)(da)，繼續向(xiang)(xiang)(xiang)西(xi)北(bei)延(yan)伸(shen)，進入亞(ya)丁灣和紅(hong)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)；中(zhong)(zhong)(zhong)(zhong)(zhong)(zhong)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)從(cong)羅德里(li)格(ge)斯島(dao)向(xiang)(xiang)(xiang)西(xi)南(nan)(nan)分(fen)出西(xi)南(nan)(nan)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)，經愛(ai)德華太子群島(dao)，接大(da)(da)西(xi)洋(yang)(yang)(yang)(yang)(yang)一(yi)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)；中(zhong)(zhong)(zhong)(zhong)(zhong)(zhong)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)至圣波(bo)爾島(dao)向(xiang)(xiang)(xiang)東(dong)(dong)(dong)(dong)(dong)南(nan)(nan)連接東(dong)(dong)(dong)(dong)(dong)南(nan)(nan)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)，再(zai)向(xiang)(xiang)(xiang)東(dong)(dong)(dong)(dong)(dong)連接太平洋(yang)(yang)(yang)(yang)(yang)一(yi)南(nan)(nan)極海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)和東(dong)(dong)(dong)(dong)(dong)太平洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)。印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)底(di)(di)除中(zhong)(zhong)(zhong)(zhong)(zhong)(zhong)脊海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)外，還有(you)許多近(jin)似南(nan)(nan)北(bei)向(xiang)(xiang)(xiang)的(de)(de)構造(zao)帶(dai)。這些(xie)構造(zao)帶(dai)相互平行，綿(mian)延(yan)很遠，其(qi)中(zhong)(zhong)(zhong)(zhong)(zhong)(zhong)東(dong)(dong)(dong)(dong)(dong)印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)，走(zou)向(xiang)(xiang)(xiang)與東(dong)(dong)(dong)(dong)(dong)經90°經線一(yi)致(zhi)，是世界上較直(zhi)的(de)(de)一(yi)條海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)。它北(bei)起北(bei)緯10°附近(jin)的(de)(de)安達曼群島(dao)，南(nan)(nan)至南(nan)(nan)緯3l° 的(de)(de)斷(duan)(duan)(duan)裂海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)，長約(yue)5 000千米(mi)，東(dong)(dong)(dong)(dong)(dong)西(xi)寬(kuan)約(yue)150-250千米(mi)。由(you)于(yu)(yu)它沿著東(dong)(dong)(dong)(dong)(dong)經90°分(fen)布，故又叫東(dong)(dong)(dong)(dong)(dong)經90° 海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)或卡彭(peng)特(te)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)。大(da)(da)洋(yang)(yang)(yang)(yang)(yang)中(zhong)(zhong)(zhong)(zhong)(zhong)(zhong)脊呈(cheng)“入”字形(xing)，將印(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)分(fen)成(cheng)三個海(hai)(hai)(hai)(hai)(hai)(hai)(hai)域。
印度洋屬海(hai)較少。內海(hai)有(you)(you)(you)紅海(hai)和(he)(he)波斯(si)灣(wan)(wan)；邊(bian)緣海(hai)有(you)(you)(you)西北(bei)(bei)部的阿拉(la)(la)(la)伯海(hai)，東北(bei)(bei)部的安(an)達曼海(hai)，東部的帝汶海(hai)和(he)(he)阿拉(la)(la)(la)弗拉(la)(la)(la)海(hai)；大(da)(da)海(hai)灣(wan)(wan)有(you)(you)(you)西北(bei)(bei)部的亞(ya)丁灣(wan)(wan)和(he)(he)阿曼灣(wan)(wan)，東北(bei)(bei)部的孟加拉(la)(la)(la)灣(wan)(wan)，澳大(da)(da)利亞(ya)北(bei)(bei)面(mian)的卡奔塔利亞(ya)灣(wan)(wan)（Carpentaria）、南面(mian)的大(da)(da)澳大(da)(da)利亞(ya)灣(wan)(wan)。在(zai)南極洲海(hai)域(yu)也有(you)(you)(you)一(yi)些屬海(hai)。海(hai)岸線除(chu)北(bei)(bei)部比較曲折之(zhi)外，大(da)(da)部分平(ping)直，少島(dao)(dao)(dao)嶼。大(da)(da)島(dao)(dao)(dao)有(you)(you)(you)馬達加斯(si)加島(dao)(dao)(dao)、索(suo)科特(te)拉(la)(la)(la)（Socotra）島(dao)(dao)(dao)、斯(si)里蘭(lan)卡島(dao)(dao)(dao)，還(huan)有(you)(you)(you)塞席爾群(qun)島(dao)(dao)(dao)；火山(shan)島(dao)(dao)(dao)有(you)(you)(you)科摩羅（Comoros）群(qun)島(dao)(dao)(dao)、馬斯(si)克(ke)林（Mascarene）群(qun)島(dao)(dao)(dao)和(he)(he)凱(kai)爾蓋朗(lang)（Kerguelen）群(qun)島(dao)(dao)(dao)；珊(shan)瑚島(dao)(dao)(dao)有(you)(you)(you)馬爾代夫(fu)群(qun)島(dao)(dao)(dao)。大(da)(da)陸(lu)(lu)(lu)邊(bian)緣地帶(dai)包(bao)括(kuo)大(da)(da)陸(lu)(lu)(lu)棚(peng)和(he)(he)大(da)(da)陸(lu)(lu)(lu)坡。大(da)(da)陸(lu)(lu)(lu)棚(peng)一(yi)般比較狹窄(zhai)，大(da)(da)陸(lu)(lu)(lu)棚(peng)較寬(kuan)的海(hai)域(yu)有(you)(you)(you)阿拉(la)(la)(la)伯海(hai)、安(an)達曼海(hai)、孟加拉(la)(la)(la)灣(wan)(wan)和(he)(he)大(da)(da)澳大(da)(da)利亞(ya)灣(wan)(wan)，寬(kuan)處在(zai)澳大(da)(da)利亞(ya)至新幾內亞(ya)島(dao)(dao)(dao)之(zhi)間(jian)，約965千米。大(da)(da)陸(lu)(lu)(lu)坡陡峻之(zhi)處坡度10°-30°，一(yi)般坡度較小。在(zai)印度河、恒河入(ru)海(hai)口外的海(hai)域(yu)，有(you)(you)(you)面(mian)積(ji)寬(kuan)廣的水下沖積(ji)扇(shan)，被水下峽谷所(suo)切(qie)割。
島(dao)(dao)(dao)弧帶(dai)從(cong)緬甸至澳(ao)大(da)(da)(da)(da)利亞延(yan)伸達5150千(qian)米，可分為兩列(lie)平行(xing)的(de)(de)島(dao)(dao)(dao)鏈：內(nei)弧屬火山島(dao)(dao)(dao)，有大(da)(da)(da)(da)、小(xiao)巽他群島(dao)(dao)(dao)（包括蘇門答臘島(dao)(dao)(dao)、爪(zhua)哇(wa)島(dao)(dao)(dao)、帝(di)汶(wen)島(dao)(dao)(dao)等）；外弧為非火山島(dao)(dao)(dao)，有安(an)達曼群島(dao)(dao)(dao)、尼科巴(ba)（Nicobar）群島(dao)(dao)(dao)、明打威(wei)（Mentawai）群島(dao)(dao)(dao)等。島(dao)(dao)(dao)弧的(de)(de)外緣——爪(zhua)哇(wa)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)溝為印(yin)(yin)(yin)度(du)(du)(du)洋(yang)(yang)水域，深(shen)點(dian)7450米。印(yin)(yin)(yin)度(du)(du)(du)洋(yang)(yang)中(zhong)(zhong)央(yang)的(de)(de)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)可分為3支(zhi)(zhi)(zhi)：北支(zhi)(zhi)(zhi)為阿(a)拉伯——印(yin)(yin)(yin)度(du)(du)(du)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)；西(xi)南(nan)支(zhi)(zhi)(zhi)為印(yin)(yin)(yin)度(du)(du)(du)洋(yang)(yang)西(xi)南(nan)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)，它與大(da)(da)(da)(da)西(xi)洋(yang)(yang)——印(yin)(yin)(yin)度(du)(du)(du)洋(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)相(xiang)連；東(dong)南(nan)支(zhi)(zhi)(zhi)為中(zhong)(zhong)印(yin)(yin)(yin)度(du)(du)(du)洋(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)，它與印(yin)(yin)(yin)度(du)(du)(du)洋(yang)(yang)東(dong)南(nan)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)相(xiang)接。北支(zhi)(zhi)(zhi)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)和(he)西(xi)南(nan)支(zhi)(zhi)(zhi)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)是結構復雜的(de)(de)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)底山脈，寬度(du)(du)(du)400-970千(qian)米，相(xiang)對高度(du)(du)(du)1830-3050米，海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)的(de)(de)中(zhong)(zhong)脊為裂(lie)谷帶(dai)，地(di)貌極為崎(qi)嶇險峻；東(dong)南(nan)支(zhi)(zhi)(zhi)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)從(cong)中(zhong)(zhong)印(yin)(yin)(yin)度(du)(du)(du)洋(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)至阿(a)姆斯特丹島(dao)(dao)(dao)的(de)(de)寬度(du)(du)(du)達1450千(qian)米，裂(lie)谷很(hen)少。印(yin)(yin)(yin)度(du)(du)(du)洋(yang)(yang)中(zhong)(zhong)央(yang)的(de)(de)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)被大(da)(da)(da)(da)小(xiao)不(bu)一的(de)(de)斷(duan)(duan)裂(lie)帶(dai)所切割，例(li)如歐文斷(duan)(duan)裂(lie)帶(dai)，即延(yan)伸至阿(a)拉伯海(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)(pen)(pen)和(he)索(suo)馬(ma)利海(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)(pen)(pen)，海(hai)(hai)(hai)(hai)(hai)(hai)(hai)底巖層位移達320千(qian)米。印(yin)(yin)(yin)度(du)(du)(du)洋(yang)(yang)東(dong)部(bu)(bu)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)域1962年發現(xian)的(de)(de)東(dong)印(yin)(yin)(yin)度(du)(du)(du)洋(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)（或稱「東(dong)經九十度(du)(du)(du)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)」），南(nan)北直線延(yan)伸約4990千(qian)米，為印(yin)(yin)(yin)度(du)(du)(du)洋(yang)(yang)中(zhong)(zhong)較長較直的(de)(de)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)。海(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)之(zhi)間為一系列(lie)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)(pen)(pen)︰北部(bu)(bu)和(he)西(xi)北部(bu)(bu)有阿(a)拉伯海(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)(pen)(pen)、索(suo)馬(ma)利海(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)(pen)(pen)；中(zhong)(zhong)部(bu)(bu)自西(xi)而東(dong)，有馬(ma)達加斯加海(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)(pen)(pen)、中(zhong)(zhong)印(yin)(yin)(yin)度(du)(du)(du)洋(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)(pen)(pen)、科科斯海(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)(pen)(pen)和(he)北澳(ao)大(da)(da)(da)(da)利亞海(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)(pen)(pen)；南(nan)部(bu)(bu)重(zhong)要(yao)的(de)(de)是克(ke)羅澤（Crozet）海(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)(pen)(pen)。根據大(da)(da)(da)(da)陸漂(piao)(piao)移學說(shuo)，印(yin)(yin)(yin)度(du)(du)(du)洋(yang)(yang)是在中(zhong)(zhong)生代(dai)（距今6500萬(wan)-22500萬(wan)年前）南(nan)半球(qiu)貢德瓦(wa)納(na)古陸解體時，印(yin)(yin)(yin)度(du)(du)(du)、澳(ao)大(da)(da)(da)(da)利亞大(da)(da)(da)(da)陸、南(nan)極大(da)(da)(da)(da)陸、非洲大(da)(da)(da)(da)陸和(he)南(nan)美大(da)(da)(da)(da)陸的(de)(de)漂(piao)(piao)移而形(xing)成的(de)(de)。
