(Greek: “gateway”), in modern construction, any tower that gives support, such as the steel towers between which electrical wires are strung, the piers of a bridge, or the columns from which girders are hung in certain types of structural work. Originally, pylons were any monumental gateways or tower-like structures.

Ancient pylons were most often massive stone structures that flanked the doors to temples. The Egyptians made frequent use of them, usually in the form of foreshortened pyramids to mark the entrances of tombs. Pylons were decorated with carvings, moldings, and cornices. The Pont Alexandre III in Paris features pylons in the form of decorative quadrangle pillars. The word may also refer to any isolated tower, especially serving monumental purposes.