Kallen Stadtfeld (カレン・シュタットフェルト, Karen Shutattoferuto) is a fictional character in the Sunrise anime series Code Geass: Lelouch of the Rebellion. In the series, she is legally known by "Kallen Stadtfeld" at school, but prefers her mother's maiden surname, using Kallen Kozuki (紅月カレン, Kōzuki Karen) during her revolutionary activities. Her voice actress Ami Koshimizu won "Best Actress in a Supporting Role" for her role as Kallen at the first Seiyu Awards in 2007. Kallen was awarded 8th place in the 29th Anime Grand Prix, then 17th and 16th, respectively, in the following two.
Kallen Stadtfeld is half Britannian, half Japanese, but believes herself to be a Japanese person at heart and prefers to be known by her mother's maiden name, Kozuki. Her father is Britannian and her mother is an Eleven; her father comes from a prestigious Britannian family, which Kallen benefits from. She attends the Ashford Academy, where she later becomes a member of its student council and is one of its most outstanding students. Her brother, Naoto Kozuki (紅月ナオト, Kōzuki Naoto), with whom she had a deep connection, was a former leader of her resistance cell before his death.