The appointment was approved during a hearing on Friday, according to documents obtained by the PA news agency.
Lisa Marie Presley died on January 12 at the age of 54 and was laid to rest at her father’s Graceland mansion in Memphis, Tennessee, on January 22.
Four days after the funeral, her mother Priscilla filed court documents disputing a 2016 amendment to Lisa Marie’s living trust.
The amendment removed Priscilla Presley and a former business manager as trustees and replaced them with her two eldest children – Riley and Benjamin Keough.
Priscilla Presley and Riley Keough agreed to a settlement in May.
Keough was officially named as sole trustee by judge Lynn Healey Scaduto during a hearing at Los Angeles Superior Court on Friday.
Earlier this month a Los Angeles coroner ruled that Lisa Marie Presley had died of complications from weight loss surgery she had several years ago.
Her death was ruled as being from natural causes due to the effects of a small bowel obstruction.