In human sexual behavior, foreplay is a set of intimate psychological and physical acts between two or more people meant to increase sexual excitement. Foreplay takes place before sexual intercourse or another act meant to induce mutual sexual orgasm.

Psychologically, foreplay lowers inhibitions and increases the arousing comfort of the partners. Physically, it stimulates the process, which produces an erection in men, allowing them to penetrate an orifice. In women, it helps stimulate the process, which leads to vaginal lubrication, allowing penetration to take place comfortably.

Whether an act constitutes foreplay depends on the intention. If no intimate sexual acts are intended, foreplay-type actions are generally classified as flirting or, in colloquial terms, being "touchy-feely".

Foreplay is often delicate in its initial stages. Even before the partners are together, foreplay can be usually introduced by the selection and creation of a particular environment. A romantic, intimate, or openly sexual atmosphere can be considered a gesture of foreplay.

Foreplay can start with non-physical behavior that signals sexual availability. Verbally, foreplay may include sexual compliments, subtle comments with two-sided entendre, and intimate conversations. Non-verbally, foreplay can include provocative clothing, licking, preening gestures, or biting one's lips, standing inside a partner's personal space, and holding a gaze longer than is acceptable for casual links.

If the partner accepts the sexual invitation, foreplay has begun. Reciprocating with similar behavior often indicates acceptance. Since these interactions are non-explicit, there can be misunderstandings about whether an invitation has been accepted or extended. Inadvertent or not, this kind of miscommunication is termed as "leading someone on".

Foreplay ultimately turns physical. Simple and seemingly harmless acts, such as straightening someone's clothing or hair, bumping into someone while walking, stroking someone's arm, or whispering in someone's ear can constitute foreplay. One may also hold hands, touch the face, "bite", kiss, or massage.

As comfort increases, the level of intimacy increases. More intimate examples include the following:

Deep tongue kissing, also popularly known as French kissing; Touching and massaging erogenous areas over clothing, also known colloquially as groping or petting; Touching and massaging erogenous areas under clothing, or heavy-petting; Rubbing together erogenous areas over clothing, also known as dry humping or grinding; Undressing oneself or partner, known as stripping; Direct manipulation of naked erogenous areas is almost always considered foreplay. In women, this includes stimulation of the clitoris and vulva whereas in men, it includes stimulation of the penis and scrotum. For both sexes, it includes arousal of nipples and anus. Stimulation can be achieved by mouth, hands, sex toys like dildos or vibrators, or common household objects like ice cubes or feathers.

Safe sex practices should only be incorporated as part of foreplay. A condom or dental dam can be applied in a playful way as part of the final stages of foreplay. Foreplay gradually tends to become purely physical and intense. It reaches its peak just before intercourse, when it induces a strong mutual desire for penetration. Some genital teasing will take place for a brief time.

Direct manipulation of naked erogenous areas is not considered foreplay when it is not preparatory for further sexual acts. For example, mutual masturbation and oral sex are considered final sexual acts; as final acts with no expectation of further sexual congress, these are not considered foreplay.