Tatlin’s Tower or The Monument to the Third International is a grand monumental building envisioned by the Russian artist and architect Vladimir Tatlin, but never built. It was planned to be erected in Petrograd (now St. Petersburg) after the Bolshevik Revolution of 1917, as the headquarters and monument of the Comintern (the third international).

Tatlin's Constructivist tower was to be built from industrial materials: iron, glass and steel. In materials, shape, and function, it was envisaged as a towering symbol of modernity. It would have dwarfed the Eiffel Tower in Paris. The tower's main form was a twin helix which spiraled up to 400 m in height, around which visitors would be transported with the aid of various mechanical devices. The main framework would contain four large suspended geometric structures. These structures would rotate at different rates of speed. At the base of the structure was a cube which was designed as a venue for lectures, conferences and legislative meetings, and this would complete a rotation in the span of one year. Above the cube would be a smaller pyramid housing executive activities and completing a rotation once a month. Further up would be a cylinder, which was to house an information centre, issuing news bulletins and manifestos via telegraph, radio and loudspeaker, and would complete a rotation once a day. At the top, there would be a hemisphere for radio equipment. There were also plans to install a gigantic open-air screen on the cylinder, and a further projector which would be able to cast messages across the clouds on any overcast day.

Vladimir Yevgrafovich Tatlin (Russian: Влади́мир Евгра́фович Та́тлин) (December 28 [O.S. December 16] 1885 – May 31, 1953) was a Russian and Soviet painter and architect. With Kazimir Malevich he was one of the two most important figures in the Russian avant-garde art movement of the 1920s, and he later became the most important artist in the Constructivist movement. He is most famous for his attempts to create the giant tower, The Monument to the Third International.

Tatlin was born in Kharkov, Ukraine, Russian Empire, the son of a railway engineer and a poet. He worked as a merchant sea cadet and spent some time abroad. He began his art career as an icon painter in Moscow, and attended the Moscow School of Painting, Sculpture and Architecture. He was also a professional musician-bandurist, and performed as such at the Paris World Fair in 1906.

Tatlin achieved fame as the architect who designed the huge Monument to the Third International, also known as Tatlin's Tower. Planned in 1920, the monument, was to be a tall tower in iron, glass and steel which would have dwarfed the Eiffel Tower in Paris (the Monument to the Third International was a third taller at 1,300 feet high). Inside the iron-and-steel structure of twin spirals, the design envisaged three building blocks, covered with glass windows, which would rotate at different speeds (the first one, a cube, once a year; the second one, a pyramid, once a month; the third one, a cylinder, once a day). High prices prevented Tatlin from executing the plan, and no building such as this was erected in his day.