苏木亚科（学名：Caesalpinioideae）又被称为云实亚科，是豆科的一个亚科，都是木本，有乔木也有灌木，大约有150属2200种，广泛分布在全世界热带和亚热带地区，尤其是在新热带界和非洲，中国有20属约100余种。有些植物学家也将这个亚科看作一个独立的科（Caesalpiniaceae）。花序总状，稍微呈两侧对称，分离，上升覆瓦状排列，5枚左右对称的花瓣，雄蕊10或较少，多数分离。如阿勃勒、洋紫荆、黄槐、羊蹄甲、决明、苏木。此亚科的模式属为苏木属（Caesalpinia）。

Caesalpinioideae is a botanical name at the rank of subfamily, placed in the large family Fabaceae or Leguminosae. Its name is formed from the generic name Caesalpinia. It is known also as the peacock flower family.

The Caesalpinioideae are mainly trees distributed in the moist tropics, but include such temperate species as the honeylocust (Gleditsia triacanthos), Kentucky coffeetree (Gymnocladus dioicus), and redbud (Cercis canadensis). Their flowers are zygomorphic, but are very variable. Nodulation is rare in this subfamily, and where it does occur, nodules have a primitive structure.