虹湾(拉丁语:"Sinus Iridum")是月球上雨海西北侧的一处月海区，位于一座直径约260公里的撞击坑中。它是被最早看见、最美丽的月海也是天文爱好者最爱的观察对象。

"虹湾"的现代名称最早是在1651年由乔万尼·里乔利提出，1935年被国际天文学联合会批准采纳。虹湾的字面意思是“彩虹之湾”。

在此之前，该月湾的其它名称有：1641年"米迦勒·弗洛伦特·范·朗伦"(Michel Florent van Langren)称它为"几何湾"(Sinus Geometricus)；而在1647年约翰·赫维留将它命名为"阿波罗湾"(Sinus Appollinis)，该名字来源于相邻月岬(可能是拉普拉斯岬)，赫维留按用地球地名命名月球对象的习惯称它为"阿波罗岬"(Promontorium Apollinis)，摩洛哥人对"三叉岬"(Cape Three Forks)的旧称。

Sinus Iridum (Latin for "Bay of Rainbows") is a plain of basaltic lava that forms a northwestern extension to the Mare Imbrium on Earth's moon. It is surrounded from the northeast to the southwest by the Montes Jura range. The protruding part of the range at the southwest end is named Promontorium Heraclides, while that at the northeast end is called Promontorium Laplace. This bay and the surrounding mountains is considered one of the most beautiful features on the Moon, and is a favorite among lunar observers.