A ball gown, ballgown or gown is a type of evening gown worn to a ball or a formal event. Most versions are cut off the shoulder with a low décolletage, exposed arms, and long bouffant styled skirts. Such gowns are typically worn with an opera-length white gloves, vintage jewelry or couture, and a stole, cape, or cloak in lieu of a coat. Where "state decorations" are to be worn, they are on a bow pinned to the chest, and married women wear a tiara if they have one. Although synthetic fabrics are now sometimes used, the most common fabrics are satin, silk, taffeta and velvet with trimmings of lace, pearls, sequins, embroidery, ruffles, ribbons, rosettes and ruching.

An evening gown, evening dress or gown is a long dress usually worn at formal occasions. The drop ranges from ballerina, tea, to full-length. Such gowns are typically worn with evening gloves. Evening gowns are usually made of luxurious fabrics such as chiffon, velvet, satin, or organza. Silk is a popular fibre for many evening gowns. Although the terms are used interchangeably, ball gowns and evening gowns differ in that a ball gown will always have a full skirt and a fitted bodice, while an evening gown can be any silhouette—sheath, mermaid, fit and flare, A-line, or trumpet-shaped—and may have straps, halters or even sleeves.