A thin film transistor, an array substrate, a display panel and a display device are provided, which is related to the field of display technologies. A thin film transistor comprises: a substrate; at least two active layers on the substrate, each active layer comprising a first terminal and a second terminal opposite to each other; a source and a drain above the substrate. The first terminal of each of the at least two active layers is electrically connected to the source, and the second terminal of each of the at least two active layers is electrically connected to the drain, and the at least two active layers are arranged on an upper surface of the substrate and separated from one another.