Kim Mai Guest is an American voice actress known for her extensive work in animation, anime, and video games. She was born on August 5, 1969, in Illinois. Her interest in acting began in childhood, participating in school plays and later working in theatre after college. She eventually moved to Los Angeles, where she joined a children's theatre group.

Her entry into voice acting came after taking a class with Kris Zimmerman, a prominent voice director. Zimmerman subsequently hired her for the role of Mei Ling in the influential video game Metal Gear Solid. Guest was reportedly the second choice for the part, as producers were initially hesitant to cast an inexperienced voice actress. She secured the role after learning a Chinese accent for the character in just three days, and it became one of her most famous performances. She would reprise the role of Mei Ling in several subsequent installments of the Metal Gear series.

In anime, Guest has voiced a wide array of characters across numerous series. A significant early role was Subaru in the 2002 series.hack//SIGN. She is also recognized for her work in the Code Geass franchise. She voiced both Nina Einstein, a student at Ashford Academy, and Sayoko Shinozaki, the family's maid, in the English adaptation of the anime series. She later returned to these roles for the 2019 film Code Geass: Lelouch of the Re;surrection and the 2024 series Code Geass: Rozé of the Recapture. Other notable anime credits include roles in Ghost in the Shell: Stand Alone Complex, Witch Hunter Robin, and Marvel Anime: Blade.

Beyond anime, Guest has contributed her voice to a wide range of Western animated series. Her television animation work includes roles in Justice League and Justice League Unlimited as characters like Katma Tui and Silver Banshee, Avatar: The Last Airbender as Song, and Ben 10 as Lucy. She has also voiced characters in series such as Rocket Power, Codename: Kids Next Door, and G.I. Joe: Renegades.

Guest's voice acting career is particularly prolific in the video game industry. In addition to her iconic role as Mei Ling, she has voiced characters in many major titles. These include Lian Xing in the Syphon Filter series, Shalua Rui in Dirge of Cerberus -Final Fantasy VII-, Tio in Grandia II, Mayu Amakura in Fatal Frame II: Crimson Butterfly, and Dawn Star in Jade Empire. She also provided voices for characters in popular franchises such as Xenosaga Episode II,.hack//Mutation, and Tales of Symphonia.

Throughout her career, Guest has also worked under different names, including Kim Guest, Kim Mai Nguyen, Kim Nguyen, and Therese Nguyen, particularly in her early work. Her body of work demonstrates a versatile vocal range, contributing to a vast number of projects across different media over several decades.