Pin-up girls or pin-up models are models whose mass-produced pictures see wide appeal as pop culture. A pin-up is intended for informal display and are found everywhere from matchbook covers to centerfolds to calendars. Pin-up girls are often glamour models, fashion models, and actresses - and some pinups are creations of an artist.”Pin-up” may also refer to drawings, paintings and other illustrations done in emulation of photos of models. The term was first attested to in English in 1941; however the practice is documented back at least to the 1890s. The “pin up” images could be cut out of magazines or newspapers, or be from postcard or chromo-lithographs, and so on. Such photos often appear on calendars, which are meant to be pinned up anyway. Later, posters of “pin-up girls” were mass-produced.

Many “pin ups” were photographs of celebrities who were considered sex symbols. One of the most popular early pin-up girls was Betty Grable. Her poster was ubiquitous in the lockers of G.I.s during World War II. Others pin-ups were artwork, often depicting idealized versions of what some thought a particularly beautiful or attractive woman should look like. An early example of the latter type was the Gibson girl, drawn by Charles Dana Gibson. The genre also gave rise to several well-known artists specializing in the field, including Alberto Vargas and George Petty, and numerous lesser artists such as Art Frahm.

The term “cheesecake” is synonymous with “pin-up photo”. The earliest documented print usage of this sense of “cheesecake” is in 1934, predating “pin-up”, although anecdotes say the phrase was in spoken slang some 20 years earlier, originally in the phrase (said of a pretty woman) “better than cheesecake”.