小白菜（学名：Brassica rapa chinensis，异名Brassica campestris chinensis或Brassica chinensis）是一种原产东亚的蔬菜，俗称青菜，又称不结球白菜、胶菜、瓢儿菜、瓢儿白、油菜（中国东北地区）、油白菜等，与大白菜（结球白菜）是近亲，同属芸苔一种，和西方的圆白菜也较近，同属十字花科芸苔属。

在英语中，小白菜按粤语“白菜”发音译作bok choy（或pak/buk choi），而大白菜则是napa cabbage。

Bok choy or pak choi (Chinese:白菜; Brassica rapa subsp. chinensis) is a type of Chinese cabbage. Chinensis varieties do not form heads; instead, they have smooth, dark green leaf blades forming a cluster reminiscent of mustard or celery. Chinensis varieties are popular in southern China and Southeast Asia. Being winter-hardy, they are increasingly grown in Northern Europe. This group was originally classified as its own species under the name Brassica chinensis by Linnaeus.