The school tie and the old school tie are a style of necktie which are British institutions particularly associated with public schools.

A school tie indicates membership of a particular school, and sometimes of a particular house in that school.

An old school tie is a tie that, on leaving school, former pupils are often entitled to wear, in their school or old-boy club colours. According to protocol, it may only be worn by former pupils. This symbol can be a discrete passport to the old boy network, and such ties can be an indication of one's social standing. Conversely, wearing a tie to which you have no right is a serious social gaffe.

Although originally an institution of male-only schools, some schools of mixed or female-only membership do present their female leavers with a tie or other equivalent. Alternative clothing such as socks, scarfs pyjamas and even underwear may also be available in the old-boy colours.

Exclusive ties are not limited to British public schools: they are also a practice of some private schools in Australia, many clubs, military regiments and colleges of universities such as Oxford and Cambridge, and have also spread to some of Britain's former imperial possessions, including Canada and the United States.