Gate-all-around integrated circuit structures having adjacent structures for sub-fin electrical contact are described. For example, an integrated circuit structure includes a semiconductor island on a semiconductor substrate. A vertical arrangement of horizontal nanowires is above a fin protruding from the semiconductor substrate. A channel region of the vertical arrangement of horizontal nanowires is electrically isolated from the fin. The fin is electrically coupled to the semiconductor island. A gate stack is over the vertical arrangement of horizontal nanowires.