Public health officials said the death of the Lancaster, Los Angeles, child is "a devastating reminder that COVID-19 infects people of all ages."
LA County health officials wrote in a press release on Tuesday that the minor was one of three new deaths.
The officials said: "One of the individuals was a youth under the age of 18."
Dr Barbara Ferrer, Los Angeles County Public Health Director, said: "Each loss we experience in LA County is tragic, and we are sending our heartfelt condolences to the families and loved ones who've had to endure this tragedy.