A transmission tower (also electricity pylon, hydro tower in Canada, and pylon in Britain) is a tall structure, usually a lattice tower made of steel that is used to support an overhead power line. In electrical grids, transmission towers carry high-voltage transmission lines that transport bulk electric power from generating stations to electrical substations, from which electricity is delivered to end consumers; moreover, utility poles are used to support lower-voltage sub-transmission and distribution lines that transport electricity from substations to electricity customers.

There are four categories of transmission towers: (i) the suspension tower, (ii) the dead-end terminal tower, (iii) the tension tower, and (iv) the transposition tower.[1] The heights of transmission towers range from 15 to 55 m (49 to 180 ft);[1] the tallest are the 380 m (1,247 ft) transmission towers of a 2,656 m (8,714 ft) span of the Jintang-Cezi Overhead Powerline Link, between the islands Jintang and Cezi in Zhejiang province, China. The longest span of a hydroelectric crossing is the Ameralik Span of the powerline crossing of Ameralik fjord, with a length of 5,376 m (17,638 ft). More transmission towers are needed to mitigate climate change, so in the 2020s transmission towers became politically important.

Transmission line towers are usually classified according to shape, including glass type, cat head type, upper type, dry type and bucket type. According to its functions, there are tension transmission line towers, suspension transmission line towers, corner transmission line towers, terminal corner transmission line towers (dead end towers), river crossing towers, etc.