A thin film transistor, a thin film transistor array panel including the same, and a method of manufacturing the same are provided, wherein the thin film transistor includes a channel region including an oxide semiconductor, a source region and a drain region connected to the channel region and facing each other at both sides with respect to the channel region, an insulating layer positioned on the channel region, and a gate electrode positioned on the insulating layer, wherein an edge boundary of the gate electrode and an edge boundary of the channel region are substantially aligned.