A fan-out semiconductor package includes: a support wiring structure including a support wiring conductive structure, a plurality of support wiring insulating layers including a first support wiring insulating layer having a recess area and a second support wiring insulating layer on the first support wiring insulating layer and enveloping the support wiring conductive structure, a pad layer enveloped by the second support wiring insulating layer and connected to the support wiring conductive structure, and an under-bump metallurgy (UBM) layer enveloped by the first support wiring insulating layer and connected to the pad layer; and a semiconductor chip on the support wiring structure, wherein the UBM layer includes a body portion and a protrusion protruding from the body portion and arranged in the recess area.