Alexandra Haefelin is a voice actor known for her work in the Japanese anime franchise Magical Girl Lyrical Nanoha. Born in London in 1975, she moved to Japan in 1996. While information about her broader career is limited, her voice roles are consistently tied to this specific series, where she provides voices for magical artifacts known as Devices that speak German.

Her most prominent role is the voice of the Book of Darkness in the series Magical Girl Lyrical Nanoha A's and its film adaptation, Magical Girl Lyrical Nanoha the Movie 2nd A's. In the movie version, this character is also referred to as NachtWal. The Book of Darkness is a central character in the A's season, a sentient and powerful Lost Logia with a corrupted defense program.

Beyond the Book of Darkness itself, Haefelin has voiced other Devices within the same fictional universe. She is the voice of Klarwind, the Armed Device used by the character Shamal, in both the A's and StrikerS television series and The Movie 2nd A's. Additionally, she provided the voice for Zest's Spear, the Armed Device of the character Zest Grangeitz, in an episode of Magical Girl Lyrical Nanoha StrikerS. These roles collectively establish her as the vocal talent for several Ancient Belkan Devices in the Nanoha franchise, all of which are characterized by their use of the German language. No information is available about other significant voice roles, recurring collaborations outside this franchise, or formal awards or achievements.