天草群岛是日本天草滩与有明海、八代海之间的群岛。

上岛（かみしま）与下岛（しもしま）二岛是天草群岛的主岛。下岛的面积为574.01平方公里，是日本除了本州等四大岛之外的第八大岛。

• 上岛
• 下岛
• 大矢野岛
• 维和岛
• 樋岛
• 御所浦岛
• 牧岛
• 汤岛
• 永浦岛
• 长岛
• 狮子岛

Amakusa (天草), which means "Heaven's Grass," is a series of islands off the west coast of Kyushu, the southernmost of the four main islands of Japan. The largest island of the Amakusa group is Shimoshima, which is 26.5 miles long and 13.5 miles in extreme width (42.6 km × 21.7 km). It is situated at 32°20'N, 130°E, separated from the rest of Kumamoto Prefecture by the Yatsushiro Sea.