A seven-string guitar is a guitar with seven strings instead of the usual six. Such guitars are not as common as the six-string variety but a minority of guitarists have utilised them for at least 150 years. Some types of these instruments are specific to certain cultures (i.e. the Russian and Brazilian guitars).

There are eight-string and ten-string guitars in use as well, but these are even less common. There are also twelve-string guitar and they are a little more common.