Formal wear (US, Canada) and formal dress (UK, Australia, New Zealand, and other Commonwealth Realms) are the general terms for clothing suitable for formal social events, such as a wedding, formal garden party or dinner, débutante cotillion, dance, or race. The Western style of formal evening dress, characterized by black and white garments, has spread through many countries; it is almost always the standard formal social dress in countries without a formal national costume.

A dress code is a set of rules governing a certain combination of clothing; some examples are black tie and morning dress. Formal dress is the grouping of all the dress codes which govern clothes worn to formal events. The traditional rules that govern men's formal dress are strictly observed^{[by whom?]}; from these derive the evening dress variants worn on many occasions, such as high school prom dances, formal dances, and entertainment industry award programs.

The dress codes considered formal in the evening are white tie and black tie. In the UK, morning dress is standard formal day time clothing (a lounge suit being still considered informal dress), but in the US/Canada morning dress is rare, having been replaced with the stroller and then the lounge, or business suit. Morning dress, however, does remain in certain settings in Europe, Australia, and Japan.