What is the name of the changeling queen?

The name of the changeling queen is Queen Chrysalis.

Queen Chrysalis is a major antagonist in My Little Pony: Friendship Is Magic and the ruler of a hive of shapeshifting changelings. She is recognizable by her black, insect-like appearance, translucent wings, curved horn, fanged teeth, and holes in her legs.

Chrysalis first appears in the season 2 finale, “A Canterlot Wedding,” which aired in 2012. She impersonates Princess Cadance, imprisons the real Cadance, and plans to feed on Shining Armor’s love while weakening Canterlot’s defenses. Cadance and Shining Armor ultimately repel Chrysalis and her army through the power of their genuine love.

She is sometimes confused with Lord Tirek, King Sombra, or Cozy Glow because all are major villains. However, those characters are not changeling queens. Chrysalis later joins Tirek and Cozy Glow in an attempt to conquer Equestria, but the trio is defeated and turned to stone in the series finale.