A thin film transistor array panel is capable of increasing an aperture ratio and decreasing parasitic capacitance between a gate electrode and a drain electrode by reducing an area of a thin film transistor. The thin film transistor array panel includes: a substrate; a gate line disposed on the substrate and including a gate electrode; a gate insulating layer on the gate line; a semiconductive island on the gate insulating layer; a circular drain electrode on the semiconductive island; and a source electrode disposed on the semiconductive island and shaped like a circular band bent in a direction from which the drain electrode is disposed. The gate electrode may include a circular portion that is overlapped by the drain electrode and a circular sector portion that is overlapped by the source electrode.