Leoni Kristin Oeffinger is a German singer, musical performer, and voice actress born in Frankfurt am Main on May 10, 1983. Her career began in musical theater, where she performed from a young age, making her stage debut in the lead role of the musical Annie at the age of fourteen. She received formal training as a musical performer at the Performing Arts Studios in Vienna and the Hamburg School of Entertainment. Oeffinger has since built a substantial career on stage, with engagements at prominent German theaters including the Oper Kiel, the Staatstheater am Gärtnerplatz in Munich, and the Theater des Westens in Berlin. Her stage repertoire includes roles such as Belle in Die Schöne und das Biest, Mistress in Evita, and Serena Katz in Fame, as well as touring Europe as a vocalist with ABBA tribute shows and as a soloist on cruise ships.

Parallel to her stage work, Oeffinger has established herself as a prolific voice actress in German dubbing, providing the German voices for characters in numerous international films and television series. She is widely recognized as the German voice of Gabriella Montez, played by Vanessa Anne Hudgens, in the High School Musical film series, and has also voiced Ashanti in The Muppets' Wizard of Oz and Ashley Dewitt in Hannah Montana. Her voice work extends to animation, where she sang the title song for the German version of the animated series Littlest Pet Shop: Tierisch gute Freunde.

Within the anime community, Oeffinger is a prominent and highly active voice. Her extensive list of anime roles includes many of the characters mentioned by the user, such as Roxy Migurdia in Mushoku Tensei: Jobless Reincarnation, Yurin Ullen in So I'm a Spider, So What?, Mary in The Faraway Paladin, Olivia Servant in The Hidden Dungeon Only I Can Enter, Yui Nakamura in Back Street Girls: Gokudols, Kirihime Natsuno in Dog & Scissors, and Angela Balzac in the film Expelled from Paradise. Beyond these, her filmography features a wide array of other notable parts, including Amira in Rage of Bahamut: Genesis, Chisaki Hiradaira in A Lull in the Sea, Ichi Akabane in Aoharu x Machinegun, Kiriha in Tsugumomo, Mai Tokiha in My-HiME, Yurika Doujima in Witch Hunter Robin, and Eugénie de Danglars in Gankutsuou: The Count of Monte Cristo. Her work continues in current series, with roles like Monika in The Great Cleric and Reona Kisaragi in Full Dive.

Oeffinger's work is not limited to animation; she is also active in voicing characters for video games and live-action dubs. Her professional profile lists her as based in Berlin, and she is noted for her vocal versatility, with a range that includes singing for German Disney productions and various dialects. She is the younger sister of fellow singer and voice actress Marieke Oeffinger.