What is the name of Voldemort's snake (which was a Horcrux)?

The story behind the answer

Nagini is Voldemort’s loyal snake and one of his Horcruxes, meaning a fragment of his soul was hidden inside her to anchor his life. Destroying Nagini was crucial to making Voldemort mortal again; Neville Longbottom killed her with the Sword of Gryffindor during the Battle of Hogwarts, sealing Voldemort’s fate. The other options don’t fit: Bellatrix is a Death Eater, and “Viper” and “Selena” aren’t characters in the series.

Fun context: In the Fantastic Beasts films, Nagini is revealed to be a Maledictus—someone cursed to eventually become a snake permanently. Memory tip: “Naga” in many Asian mythologies means “serpent,” so “Nagini” naturally points to “the snake.”