Anthony Fauci will step down as head of the National Institute of Allergy and Infectious Diseases (NIAID) and chief medical adviser to President Joe Biden.
Dr Fauci, who served as director of the NIAID for 38 years, said he would leave both positions in December to “pursue the next chapter” of his career.
“It has been the honour of a lifetime to have led the NIAID,” Dr Fauci, 81, said in a statement.
He became the face of the nation’s Covid-19 response during the pandemic.
Yesterday, Mr Biden thanked him for his “spirit, energy, and scientific integrity”.
“The United States of America is stronger, more resilient, and healthier because of him,” the president wrote in a statement.
In July, Dr Fauci said he would retire before the end of Mr Biden’s current term.