Tungsten disulfide nanotubes (WS 2 -NTs), with their cylindrical structure composed of rolled WS 2 sheets, have attracted much interest because of their unique physical properties reflecting quasi-one-dimensional chiral structures. They exhibit a semiconducting electronic structure regardless of their chirality, and various semiconducting and optoelectronic device applications have been demonstrated. The development of techniques to fabricate arrayed WS 2 -NTs is crucial to realizing the highest device performance. Since the discovery of WS 2 -NTs, various synthesis techniques have been reported; however, horizontally arrayed WS 2 -NTs have never been successfully synthesized. Here, we demonstrate a simple technique to synthesize arrayed WS 2 -NTs. Through precise temperature and gas control, W 18 O 49 nanowires are grown along the [1̅ 101] direction on an r-plane sapphire substrate, and the nanowires are converted into nanotubes via sulfurization under optimized conditions. The demonstrated synthesis technique for arrayed WS 2 -NTs will play a central role in the fabrication of devices using transition-metal dichalcogenide nanotubes.