The Flag of Vatican City State, as per the 2023 w:en:Fundamental Law of Vatican City State, reproducing Annex A which contains the official depiction of this version. See 2023 Fundamental Law of Vatican City State, art. 23, n. 1.
This 2023 flag is very similar to the flag used in the 1929 Fundamental Law of Vatican City State, see here, p. 35. Thus, it is in the public domain.
Allegato A

Requested by and knowledge from Veverve
Goran_tek-en