The YF-21 is an experimental variable fighter featured in the Macross Plus OVA and its theatrical adaptation, Macross Plus Movie Edition. It was part of U.N. Spacy's Advanced Variable Fighter initiative under Project Super Nova. The prototype was piloted by Guld Goa Bowman.
It ultimately lost to the YF-19, although a handful of its final version were still produced under special circumstances. The YF-21 served as a prototype for the VF-22 Sturmvogel II, which later appeared in Macross 7, often used by ace pilots.