A One is the sixteenth full-length studio album recorded by Japanese singer Ayumi Hamasaki. It was released on April 8, 2015 by Avex Trax. It reached #4 on the Oricon charts.

Ayumi Hamasaki is a Japanese singer, songwriter, record producer, actress, model, spokesperson, and entrepreneur. By 2002, Hamasaki had earned the nickname "Empress of J-pop" due to her popularity in Japan and throughout Asia, as well as being referred to as "the voice of the lost generation". Due to her success and relevance throughout her career, she is considered one of the top solo female artists of the Heisei era for her influence on the music industry and various fashion trends.