Lydia Alice Jacoby (born February 29, 2004) is an American competitive swimmer specializing in breaststroke and individual medley events. She won the gold medal in the 100 meter breaststroke and the silver medal in the 4x100 meter medley relay at the 2020 Summer Olympics. She was the first swimmer from Alaska to qualify for an Olympic Games, qualifying for the 2020 Summer Olympics in the 100 meter breaststroke when she was 17 years old.