In the How to Train Your Dragon films, Astrid’s dragon is named Stormfly.
Stormfly is a Deadly Nadder, a fast and heavily armed dragon with sharp tail spines. Astrid first encounters her as a threatening dragon, but the pair eventually form a close partnership. Stormfly becomes Astrid’s main mount and appears throughout the animated film trilogy.
The dragon’s name reflects her speed and aerial power. Stormfly can fire sharp spines from her tail and has strong eyesight, abilities that make her useful in both travel and combat. Astrid’s flying gear and Stormfly’s blue coloring help distinguish them from Hiccup and Toothless.
Stormfly is sometimes mixed up with Hookfang, Snotlout’s Monstrous Nightmare, or Cloudjumper, Valka’s dragon. Those dragons belong to different characters and species. Stormfly’s species is the Deadly Nadder, not a Night Fury.