The 53rd Earth Kingdom monarch in The Legend of Korra is Hou-Ting.
Hou-Ting is the Earth Queen who rules during Book Three: Change. She is the daughter and successor of Earth King Kuei, the monarch seen in Avatar: The Last Airbender, and she inherits the title after the Earth Kingdom’s long royal line reaches its 53rd ruler.
Her reign is authoritarian and self-serving. After Harmonic Convergence creates new airbenders, Hou-Ting attempts to seize them for her military, placing her in conflict with Korra and the newly restored Air Nation. She also uses the Dai Li to suppress dissent.
Hou-Ting’s rule ends during the Red Lotus uprising in Ba Sing Se. Zaheer kills her, and the collapse of Earth Kingdom authority leads to a period of political uncertainty. Her successor, Prince Wu, later supports transforming the monarchy into a democratic Earth Federation.