The hourglass figure is one of the four traditional female body shapes described by the fashion industry; the other shapes are the rectangle, inverted triangle, and spoon (or pear). The hourglass shape is defined by a woman's body measurements – the circumference of the bust, waist and hips. Hourglass body shapes have a wide bust, a narrow waist, and wide hips with a similar measurement to that of the bust. This body shape is named for its resemblance to that of an hourglass, where the upper and lower half are wide and roughly equal while the middle is narrow in circumference, making the overall shape wide-narrow-wide.

Women who exhibit the hourglass figure have been shown to be more admired, which can put pressure on women whose body shapes are noticeably different to strive to achieve the hourglass figure. This can lead to body dissatisfaction which can cause eating disorders in (often young) women from all over the globe.

The so-called "gynecoid" pelvis is low and wide, and has a wide pubic arch. This shape is considered ideal for childbirth because women who have it can more easily deliver a child. Tall women are less likely to have the gynecoid pelvis shape. Ethnic variation has also been found, as East Asian women are more likely to have the gynecoid pelvis shape than White women.

It has been proposed by scientists that the evolutionary reason for the female body shape is due in part to this sexual selection. Sex-typical body shapes (a man's muscular physique and a woman's hourglass figure) are an outcome of evolutionary adaptation for reproductive fitness because they convey information about gene quality, health and fertility, which are important elements for mate selection.

Anthropologist Holly Dunsworth has criticised the common assumption that female body shapes evolved for the above reasons. She suggests that although sexual dimorphism may partly explain women's body shapes, they likely also reflect adaptation to reproduction and locomotion. One study found that during pregnancy, a woman's body is transformed so it is properly able to carry the baby. To prevent the center of gravity in a woman's body from being off balance, it is believed that evolution could have favored fat deposits in the gluteal region and the thighs.

A systematic review of multiple studies found that age and sex were the factors most strongly correlated with waist-hip ratio (WHR). These authors wrote that there is not enough evidence to conclude that a low WHR is a sign for health, fertility or better reproductive success. The researchers summarized their findings, stating, "WHR is a powerful measure (as shown by the numerous physical and physiological characteristics correlated with it), but it may not be as “magical” as often assumed..."

Data from 1996–2005 indicated that women with larger (> 0.5) waist-to-height ratios had a higher risk of premature death and significant health problems.

Sex hormones can influence body shape. Estrogen decreases fat accumulation to the abdominal region and stimulates fat growth in the lower body.