The Mascarene Islands (or Mascarenhas Archipelago) is a group of islands in the Indian Ocean east of Madagascar comprising Mauritius, Réunion, Rodrigues, Cargados Carajos shoals, plus the former islands of the Saya de Malha, Nazareth and Soudan banks. The collective title is derived from the Portuguese navigator Pedro Mascarenhas, who first visited them in the early sixteenth century. The islands share a common geologic origin in the volcanism of the Réunion hotspot beneath the Mascarene Plateau and form a distinct ecoregion with a unique flora and fauna.

The Islands are volcanic in origin; Saya de Malha (35 mya) was the first of the Mascarene islands to rise out of the Indian Ocean due to the Réunion hotspot, followed by Nazareth Bank (some 2,000 yrs later), Soudan Bank and Cargados Carajos. The youngest islands to form were Mauritius (7–10 mya), the oldest of the existing islands, created along with the undersea Rodrigues ridge. The islands of Rodrigues and Réunion were created in the last two million years. Réunion is the largest of the islands (2,500 km²), followed by Mauritius (1,900 km²) and Rodrigues (110 km²). Eventually Saya de Malha, Nazareth and Soudan were completely submerged, Cargados Carajos remaining as a coral atoll. The Réunion hotspot was beginning to cool and Rodrigues came out as a tiny island. Had erosion not taken place, Cargados Carajos would have been a large volcanic island, and the Mascarenes would have been an archipelago of seven or more (counting Saya De Malha, Nazareth and Soudan) large, populated islands, rather than the three (Mauritius, Reunion, Rodrigues) that remain today.