花萼是一朵花中所有萼片的总称，位于花的最外层，一般是绿色，样子类似小叶，但也有少数花的花萼样子类似花瓣，有颜色。花萼在花还是芽时包围着花，有保护作用，花开放后花萼托在最外边。每个萼片都独立分离的叫做“离萼”，如玫瑰；各个萼片全部或部分连接在一起的叫做“合萼”，如紫荆；花谢后萼片不脱落，保存在果实上叫做“宿萼”，如茄子；萼片有两层的，外面一层叫做“副萼”，如木槿。

A sepal (/ˈsɛpᵊl/ or /ˈsiːpᵊl/) is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom. The term sepalum was coined by Noël Martin Joseph de Necker in 1790, and derived from the Greek σκεπη (skepi), a covering.