A handlebar is part of the steering mechanism, in lieu of a steering wheel, for vehicles that are ridden on, such as:
Bicycle handlebar Motorcycle handlebar
Handlebar may also refer to
Handlebar moustache, a type of moustache Handlebars (template system), a JavaScript library to build semantic templates "Handlebars" (Flobots song) "Handlebars" (Jennie song)