A thin film transistor substrate includes: a substrate; and a thin film transistor including a gate electrode on the substrate, an active layer on the gate electrode, and a source electrode and a drain electrode on the active layer. Within the thin film transistor, at least one of the source electrode and the drain electrode defines a plurality of branch electrodes thereof and a main electrode to which the plurality of branch electrodes is commonly connected. Each of the plurality of branch electrodes overlaps the gate electrode.