Super Flags are achievements in Paper Mario: Sticker Star and Paper Mario: Color Splash. They mark milestones that Mario has made on his journey, and are showcased during the victory parades.
In Paper Mario: Sticker Star, eight Super Flags are found in Decalburg, near the Sticker Fest area.
In Paper Mario: Color Splash, six Super Flags can be found in Port Prisma, around the Prisma Fountain. Once every Super Flag is found, Huey is seen falling into the fountain at the end of the end credits.