What is the name of Merida's horse?

Merida’s horse is named Angus.

Angus is Merida’s powerful Clydesdale horse in Pixar’s Brave (2012). He is her trusted riding companion in the kingdom of DunBroch, a fictional medieval Scottish setting. Merida uses Angus to race across the countryside, practice her archery, and escape into the forest when tensions with her mother, Queen Elinor, reach a breaking point.

Angus reflects Merida’s adventurous and independent nature. He is large and strong enough to carry her at speed, yet he also has a spirited personality of his own. When Merida rides into the wilderness after asking a witch for a magical solution to her family conflict, Angus helps establish the story’s transition from royal life to the dangerous natural world.

The other options are horses from different Disney stories. Philippe is Belle’s horse in Beauty and the Beast, Maximus is Rapunzel’s horse in Tangled, and Khan belongs to Mulan. Angus is also distinctive because Brave was produced by Pixar, making Merida the first—and, in the Disney Princess line-up, the only—Pixar-created Disney Princess.