Also known as: 20世纪男孩, 二十世纪男孩
The stand possessed by Magenta Magenta in Steel Ball Run, Part 7 of the Jojo No Kimyou Na Bouken.
It is a defensive stand that Magenta Magenta wears around his body to redirect all damage away from himself.
Namesake is likely "20th Century Boy", a song by the British band T. Rex, released as a single in 1973 with "Free Angel" as the B-side.