A new procedure for the synthesis of MoS2 nanotubes is reported, and additionally demonstrated for MoSe2, WS2, and WSe2. Highly concentrated sunlight creates continuous high temperatures, strong temperature gradients, and extended hot annealing regions, which, together with a metallic (Pb) catalyst, are conducive to the formation of different inorganic nanotubes. Structural characterization (including atomic resolution images) reveals a three-step reaction mechanism. In the first step, MoS2 platelets react with water-air residues, decompose by intense solar irradiation, and are converted to molybdenum oxide. Subsequently, the hot annealing environment leads to the growth of Pb-stabilized MoO3-x nanowhiskers. Shortly afterward, the surface of the MoO3-x starts to react with the sulfur vapor supplied by the decomposition of nearby MoS2 platelets and becomes enveloped by MoS2 layers. Finally, the molybdenum oxide core is gradually transformed into MoS2 nanotubes. These findings augur well for similar syntheses of as yet unattained nanotubes from other metal chalcogenides.