In BDSM, a top is a partner who takes the role of master or punisher, performing such acts as bondage, flogging, humiliation, or servitude upon the bottom.

A top is not necessarily dominant, and vice versa. A service top is a person who applies sensation or control to a bottom, but does not adopt a superior persona, and does so to the bottom's explicit instruction. Likewise, a pure dominant would give orders to a submissive, but not employ any physical or psychological techniques of control.

It should be noted that the top is most often the partner who is following instructions - he or she typically tops when, and in the manner, requested by the bottom.

In order to explore BDSM sex, it is essential for a top to be very responsive to the needs, feelings, and limits of his or her bottom. Otherwise the scene can be ruined, being simply painful rather than erotic.

Note that in BDSM sex, it is commonplace for two partners to switch roles from one encounter to the other, depending on mood and preference. See switch.

In Japanese bondage and sexually-themed anime and manga (especially yaoi), a top is referred to as seme, a term from kabuki.