Ugg boots, sometimes known as ugh or ug boots, are a style of sheepskin boot, with refined wool as the inner lining and a tanned outer surface. Worn by both men and women, Ugg boots often have a synthetic, usually eva outsole, although this is not universal. Uggs are extremely popular with the teenage set, typically the classic Ugg boots short and tall worn by girls with mini skirts or with jeans tucked in.

In Australia and New Zealand, sheepskin boots have long been popular with people in rural occupations, such as sheep shearers, who have ready access to the raw materials. Ugg boots have also been sought after by surfers and competitive swimmers since the 1960s, for keeping feet warm while out of the water. The terms ugg boots, ugh boots and ug boots have been used as generic terms for sheepskin boots in Australia since the 1950s and 1960s. The natural properties of sheepskin results in well balanced thermostatic benefits. Thick fleecy fibers on the inner part of the boots allows air to circulate and keep the feet at body temperature. Man made materials and faux fur boots do not have these properties and sheepskin boots are highly prized for their effectiveness. Ugg boots are designed to be worn without socks in order to maximize the thermostatic benefits of sheepskin.