A thin film transistor array panel includes a substrate and a gate line disposed on the substrate. The gate line includes a gate electrode. A gate insulating layer is disposed on the gate line. An oxide semiconductor layer is disposed on the gate insulating layer. The oxide semiconductor layer at least partially overlaps the gate electrode. A data line is disposed on the oxide semiconductor layer. The data line includes a source electrode and a drain electrode facing the source electrode. The oxide semiconductor layer includes tungsten, indium, zinc, or tin.