The Strait of Bab-el-Mandeb or Mandeb Strait is situated between Yemen on the Arabian Peninsula, and Djibouti and Eritrea in the Horn of Africa. The Strait connects the Gulf of Aden to the Red Sea.

The distance across the Strait is about 30 kilometres, from Ras Menheli in Yemen to Ras Siyyan in Djibouti. The Strait is divided into two channels by the island of Perim, of which the eastern channel, known as the Bab Iskender or Alexander's Strait, is 3 kilometres wide and 30 metres deep, while the western channel, known as Dact-el-Mayun, has a width of about 25 kilometres and a depth of 310 metres. A group of smaller islands known as the "Seven Brothers" are also found in the Strait and lie near the coast of Djibouti.

The Bab-el-Mandeb serves as a strategic link between the Mediterranean Sea and the Indian Ocean via the Red Sea and the Suez Canal. It is estimated that over 3 million barrels of oil pass through the Strait every day, a not insignificant proportion of the 43 million barrels that is moved by tanker worldwide every day.