Thigh-high boots, known also as thigh-length boots or simply thigh boots, are boots that extend above the knees. Other terms for this footwear include over-the-knee boots (OTK boots) and, especially when cuffed, pirate boots. Lengths vary from reaching just over the knee to reaching almost to the crotch (referred to as crotch boots).
Thigh boots are made of materials ranging from various leathers to various synthetic materials (including vinyl, polyurethane, or latex) to various fabrics (such as silk or polyester microfiber). Many are constructed with zippers, but some are designed as pull-on boots. Heel heights vary, but most styles are either flat or with heels greater than 3 inches (7.5 cm). Heel styles vary from metal spikes to chunky. Like other boots, they can also have platform soles.
Thigh boots are considered by many to be erotic or kinky. They are used as fetish clothing in boot fetishism and shoe fetishism. Cheaper thigh boots are often worn by prostitutes and professional dominatrices, so many people consider them icons of such trades. Because of the latter, they are often associated with sadomasochism. Nevertheless, they are frequently sold by couture designers, perhaps because of the implied eroticism.