Portrait painting is a genre in painting, where the intent is to represent a specific human subject. The term 'portrait painting' can also describe the actual painted portrait. Portraitists may create their work by commission, for public and private persons, or they may be inspired by admiration or affection for the subject. Portraits often serve as important state and family records, as well as remembrances.

Historically, portrait paintings have primarily memorialized the rich and powerful. Over time, however, it became more common for middle-class patrons to commission portraits of their families and colleagues. Today, portrait paintings are still commissioned by governments, corporations, groups, clubs, and individuals. In addition to painting, portraits can also be made in other media such as prints (including etching and lithography), photography, video and digital art.

It may seem obvious today that a painted portrait is intended to achieve a likeness of the sitter that is recognisable to those who have seen them, and ideally is a very good record of their appearance. In fact this concept has been slow to grow, and it took centuries for artists in different traditions to acquire the distinct skills for painting a good likeness.

A well-executed portrait is expected to show the inner essence of the subject (from the artist's point of view) or a flattering representation, not just a literal likeness. As Aristotle stated, "The aim of Art is to present not the outward appearance of things, but their inner significance; for this, not the external manner and detail, constitutes true reality." Artists may strive for photographic realism or an impressionistic similarity in depicting their subject, but this differs from a caricature which attempts to reveal character through exaggeration of physical features. The artist generally attempts a representative portrayal, as Edward Burne-Jones stated, "The only expression allowable in great portraiture is the expression of character and moral quality, not anything temporary, fleeting, or accidental."

In most cases, this results in a serious, closed lip stare, with anything beyond a slight smile being rather rare historically. Or as Charles Dickens put it, "there are only two styles of portrait painting: the serious and the smirk." Even given these limitations, a full range of subtle emotions is possible from quiet menace to gentle contentment. However, with the mouth relatively neutral, much of the facial expression needs to be created through the eyes and eyebrows. As author and artist Gordon C. Aymar states, "the eyes are the place one looks for the most complete, reliable, and pertinent information" about the subject. And the eyebrows can register, "almost single-handedly, wonder, pity, fright, pain, cynicism, concentration, wistfulness, displeasure, and expectation, in infinite variations and combinations."

Portrait painting can depict the subject "full-length" (the whole body), "half-length" (from head to waist or hips), "head and shoulders" (bust), or just the head. The subject's head may turn from "full face" (front view) to profile view (side view); a "three-quarter view" ("two-thirds view") is somewhere in between, ranging from almost frontal to almost profile (the fraction is the sum of the profile [one-half of the face] plus the other side's "quarter-face"; alternatively, it is quantified 2⁄3, also meaning this partial view is more than half a face). Occasionally, artists have created composites with views from multiple directions, as with Anthony van Dyck's triple portrait of Charles I in Three Positions. There are even a few portraits where the front of the subject is not visible at all. Andrew Wyeth's Christina's World (1948) is a famous example, where the pose of the disabled woman – with her back turned to the viewer – integrates with the setting in which she is placed to convey the artist's interpretation.

Among the other possible variables, the subject can be clothed or nude; indoors or out; standing, seated, reclining; even horse-mounted. Portrait paintings can be of individuals, couples, parents and children, families, or collegial groups. They can be created in various media including oils, watercolor, pen and ink, pencil, charcoal, pastel, and mixed media. Artists may employ a wide-ranging palette of colors, as with Pierre-Auguste Renoir's Mme. Charpentier and her children, 1878 or restrict themselves to mostly white or black, as with Gilbert Stuart's Portrait of George Washington (1796).

Sometimes, the overall size of the portrait is an important consideration. Chuck Close's enormous portraits created for museum display differ greatly from most portraits designed to fit in the home or to travel easily with the client. Frequently, an artist takes into account where the final portrait will hang and the colors and style of the surrounding décor.