Kallisti is a word from the Greek language. It may be translated as "for the most beautiful one" or "to the prettiest one."

In Greek mythology, this word was inscribed on the Golden Apple of Discord by Eris, and rolled into a wedding celebration where the goddesses Hera, Athena, and Aphrodite began to quarrel as to who was the intended recipient. Paris was chosen to mediate, and gave the Apple to Aphrodite. This choice was recounted as the legendary start of the Trojan War.

The word Kallisti, written on a golden apple, is a principal symbol of Discordianism.

The word is properly spelled in Greek καλλίστῃ, but in non-philological texts (such as Discordian ones) it is usually given as καλλιστι. Most versions of Principia Discordia actually spell it as καλλιχτι, but this is definitely incorrect; in the afterword of the 1979 Loompaniacs edition of Principia, Gregory Hill says that was because on the IBM typewriter he used, not all Greek letters coincided with Latin ones and he didn't know enough of the letters to spot the mistake.

Kallisti (Καλλίστη) is also an ancient name of Santorini.