The underarm (or armpit, axilla, or oxter) is the area on the human body directly under the joint where the arm connects to the shoulder. Anatomically, the axilla is bound anteriorly by the pectoralis major and minor muscles, posteriorly by the subscapularis and the scapula, medially by the ribcage and by the serratus anterior, and laterally by the coracobrachialis and the short head of the biceps brachii.

Underarm hair usually grows in the underarms of both males and females, beginning in adolescence, though it is common in many societies for women to remove it for aesthetic reasons, while men tend to keep it. Recently many straight men in the US have begun to remove underarm hair due to popularization by hairless male models and athletes. Also see metrosexual.

Body odor develops in the underarms due in part to the waste products of microorganisms that feed on sebum, the fatty secretions produced by sebaceous glands. A wide variety of deodorant and antiperspirant products are sold for the purpose of mitigating this odor.

The underarms are among the locations in the human body which are most vulnerable to tickling.

In Scotland, northern England and Ireland the term oxter is commonly used.

The sexual attraction to the underarms is called axillism or maschalophilous.

Upper limb anatomy

Achsel | Axila | Akselo | Aisselle | Achlais | Oksel | Axila | Kainalo