Shoulder pads are a type of fabric-covered padding used in clothing to give the wearer the illusion of having broader and less sloping shoulders. In the beginning, shoulder pads were shaped as a semicircle or small triangle and were stuffed with wool, cotton, or sawdust. They were positioned at the top of the sleeve to extend the shoulder line. A good example of this is their use in "leg-o'-mutton" sleeves or the smaller puffed sleeves which are based on styles from the 1890s. In men's styles, shoulder pads are often used in suits, jackets, and overcoats, usually sewn at the top of the shoulder and fastened between the lining and the outer fabric layer. In women's clothing, their inclusion depends on the fashion taste of the day. Shoulder pads in clothing can compensate for people with narrow or sloping shoulders. They can also compensate for certain fabrics' natural properties, most notably suede blazers, due to the weight of the material. There are periods when pads intended to exaggerate the width of the shoulders are favored. As such, they were popular additions to clothing (particularly business clothing) during the 1930s and 1940s; the 1980s (encompassing a period from the late 1970s to the early 1990s); and the late 2000s to early 2010s.

In sports, the shoulder pad was invented in 1877 by a Princeton football player and was used in American football. In women's fashion, shoulder pads originally became popular in the 1930s when fashion designers Elsa Schiaparelli and Marcel Rochas included them in their designs of 1931. Though Rochas may have been the first to present them, Schiaparelli was the most consistent in promoting them during the 1930s and '40s and it is her name that came to be most associated with them. Both designers had been influenced by the extravagant shoulder flanges and small waists of traditional Southeast Asian ceremonial dress. Costume designer Travis Banton's broad-shouldered designs for Marlene Dietrich also influenced public tastes.

Soon, broad, padded shoulders dominated fashion, seen even in eveningwear and perhaps reaching a peak of variety in 1935-36, when even Vionnet showed them; Rochas presented high, pinched-up shoulders; and Piguet outdid Rochas by extending his widened shoulders vertically like oars or paddles. Amid all this competing extravagance, the widest shoulders were still said to come from Schiaparelli, who hadn't given them up even when they briefly dropped out of favor with designers in 1933.

War was in the air during this entire period, and fashion reflected it in epaulettes and other martial details, but after World War II began in 1939, women's fashions became even more militarised. Jackets, coats, and even dresses in particular were influenced by masculine styles and shoulder pads became bulkier and were positioned at the top of the shoulder to create a solid look that sloped slightly toward the neck.

The shoulder-padded style had now become universal, found in all garments except lingerie, so standard that when US designer Claire McCardell wanted to remove them from her garments in 1940, her financiers feared their sales would suffer and insisted that pads be retained. McCardell's innovative response was to put them in with very simple stitching so that they could be easily removed by the wearer, prefiguring the flexibility of the velcro-fastened shoulder pads of the 1980s. The following year, British designer Molyneux also eliminated shoulder pads, part of a prophetic trend in high fashion that would be carried further by Balenciaga in 1945 and culminate in Dior's slope-shouldered 1947 Corolle collection.

Big shoulders were still popular in 1945, when Joan Crawford wore a fur coat with wide, exaggerated shoulders, also designed by Adrian, in the film Mildred Pierce.

In men's fashion, zoot suits had their own share of popularity. Basically, a zoot suit is based on a "regular" 2-piece suit, yet one or two sizes larger, so it was supposed to be "padded like a lunatic's cell".

During this period, stiff, felt-covered cotton batting was the material used for most shoulder pads, a combination that allowed for easy adjustment but didn't hold its shape very well when washed.