Axillary is an anatomical term derived from axilla, the armpit. "Axillary" literally means "pertaining to the armpit".

In vertebrate anatomy and medicine, it occurs in terms like:

• Axillary artery
• Axillary vein
• Axillary nerve

In birds, the axillaries are the "armpit" feathers which become visible when the bird raises its wing. They can be important in distinguishing species, e.g. in the Pluvialis golden plovers.

In botany, axillary refers to the location of a node on a plant stem; more precisely, to the apical angle between a leaf and the stem above it. Almost all buds are located in axillary positions, for example.