Mariko Nagahama is a Japanese voice actress known for her work from the late 1990s through the 2010s. She is originally from Aomori Prefecture and was affiliated with the talent agency Groupimpact as well as the theatre company Alter-Ego. Her career includes a wide range of supporting and guest roles in numerous long-running anime series.

Nagahama's filmography includes appearances in several sports and shonen series from the 2000s. She voiced the role of Shingo Obata in the series Showta no Sushi, a role that appears as "new child" in the show's adaptation. In the series Whistle!, which focuses on soccer, she played the characters Ippei Toyama and Yamakawa Tomonori. She also provided the voice for the character of a nurse in the long-running series Yu-Gi-Oh! Duel Monsters.

Throughout her career, Nagahama accumulated a substantial number of credits in major anime franchises. She had recurring roles in the Yu-Gi-Oh! franchise, appearing in both the original Yu-Gi-Oh! Duel Monsters and Yu-Gi-Oh! GX. In the first series, she played several characters including the child version of the protagonist Seto Kaiba, and in GX she voiced the antagonist Miss Dorothy and the comic relief creature Ojama Yellow. She also worked on the series Whistle! and had a role in the Inspector Gadget franchise.

Beyond these noted series, Nagahama had parts in a diverse range of other popular anime. Her television credits include roles in Kochira Katsushika-ku Kameari Kōen Mae Hashutsujo (as Ryotsu Keiko), The Prince of Tennis, Mirmo!, and the romantic drama Suzuka. She also worked on the first series of the long-running property The Law of Ueki and appeared in the musical romantic comedy Full Moon o Sagashite. Her film work includes a part in Rurouni Kenshin: Reflection and the Yu-Gi-Oh! movie The Pyramid of Light. She also had a role in the web anime星空キセキ.