Princess Anne, who won the same title in 1971, cheered on jubilantly from the crowd as her 24-year-old daughter matched and then exceeded her achievement, despite only being drafted into the British team at the last minute.
Phillips took home a second gold medal when the British team won the overall team gold medal - Princess Anne entered the competition only as an individual competitor.
Following her victory, Phillips gushed, "The crowd were fantastic. I tapped quite a few fences but the horse was a good boy.
"I didn't know whether the time was all right. It is fantastic. Two golds! It's so great for the team as we didn't come in as favourites."