Risa Niigaki is a Japanese actress, singer, and former idol who began her career in the entertainment industry in 2001. She was born on October 20, 1988, in Yokohama, Kanagawa Prefecture, Japan. Niigaki is widely known for her long-standing membership and eventual leadership of the popular J-pop group Morning Musume, a role that brought her significant public attention and led to her involvement in voice acting.

Her primary and most documented voice acting credit came in 2007 for the anime television series Robby & Kerobby. Niigaki was selected to provide the voice for the character Athena. She took over this role from fellow Morning Musume member Nozomi Tsuji, who had to step down due to a pregnancy announcement. This voice acting work directly led to the formation of a new musical unit within the Hello! Project agency called Athena & Robikerottsu, which was created specifically in conjunction with the anime. Niigaki led this group, which also included Aika Mitsui from Morning Musume and Saki Nakajima and Chisato Okai from the group Cute, and they performed theme songs for the series.

This voice role represents a key instance of her acting work within animation, connecting her primary music career with a foray into voice performance. Besides this, Niigaki's acting career is extensive and includes numerous live-action roles in television dramas, films, and stage musicals. Her other notable acting credits include the film Hontouni atta Kowai Hanashi 3D, the drama Hitmaker Aku Yu Monogatari where she played a member of the duo Pink Lady, and a stage production of Cinderella in which she played the Prince.

Throughout her career, Niigaki frequently collaborated with other members of the Hello! Project agency, both in musical groups and acting projects. Her most significant and recurring collaborations were with her fifth-generation Morning Musume cohort, particularly Ai Takahashi, with whom she shared many professional milestones, including holding the record for the longest-serving members in the group's history. She also worked extensively with members of other Hello! Project groups like Cute and Berryz Koubou in various shuffle units and theatrical performances.

Among her notable achievements, Niigaki rose to become the sub-leader of Morning Musume in 2007 and later became the group's leader in 2011, a position she held until her graduation from the group and Hello! Project in May 2012. At the time of her departure, she was the longest-serving member in the history of Morning Musume. Following her graduation, Niigaki has continued her career in entertainment as an actress and singer, releasing solo work and performing in various stage productions.