The gadulka (Bulgarian: Гъдулка) is a traditional Bulgarian bowed string instrument. Alternate spellings are "gudulka" and "g'dulka". Its name comes from a root meaning "to make noise, hum or buzz". The gadulka is an integral part of Bulgarian traditional instrumental ensembles, commonly played in the context of dance music.

The gadulka commonly has three (occasionally four) main strings with up to ten sympathetic resonating strings underneath, although there is a smaller variant of the instrument in the Dobrudja region with no sympathetic strings at all. Only the main melodic strings are touched by the player's fingers and the strings are never pressed all the way down to touch the neck. The gadulka is held vertically, with the bow held perpendicular in an under-hand hold.

Gadulka is related to Russian gudok. Another possible origin of the Gadulka may be the lira, the bowed Byzantine instrument of the 9th century AD and ancestor of most European bowed instruments. Similar bowed instruments and lira descendants have continued to be played in the Mediterranean and the Balkans until the present day, for example the Lira Calabrese of Calabria, Italy; the lyra of Crete and the Dodecanese, Greece; and the Armudî kemençe in Istanbul, Turkey.