Costume Jewellery or Fashion Jewellery is jewellery that is made of less valuable materials including base metals, glass, plastic, and synthetic stones, in place of more valuable materials such as precious metals and gems. Costume jewellery is usually inexpensive, and often flashy. Its main use is in fashion, as opposed to "real" jewellery which may be regarded as collectibles or investments.

While Costume and Fashion Jewellery is inexpensive, it can be difficult to tell the difference between Costume and Fashion Jewellery items and "real" jewellery.