Kamala Harris has made history as the first female, first black and first Asian-American US vice-president.
She was sworn in just before Joe Biden took the oath of office to become the 46th US president.
Ms Harris, who is of Indian-Jamaican heritage, initially ran for the Democratic nomination.
But Mr Biden won the race and chose Ms Harris as his running mate, describing her as "a fearless fighter for the little guy".
Prior to taking the oath at the US Capitol, Ms Harris paid tribute to the women who she says came before her. "I stand on their shoulders," she said in a video.
Eugene Goodman, the Capitol police officer who was hailed as a hero for steering a pro-Trump mob away from Senate chambers during the 6 January riot, escorted Ms Harris at the inauguration.