Mackenyu was born in Los Angeles, November 16, 1996, and is the son of actor, producer, director, and martial artist Shin'ichi Chiba. Growing up in Los Angeles, he appeared in a few films and TV shows while he was in school and had many interests that included learning to ride horseback, Kyokushin Karate, gymnastics, water polo, and wrestling as well as interest in music that led him to learn piano at age ten and later learning to play saxophone and flute.

Mackenyu rose to fame as an actor after landing the role of Wataya Arata in the Chihayafuru trilogy (2016) that earned him the 40th Annual Japan Academy Newcomer of the Year Award in 2017. His fame grew dramatically after his supporting role as Cadet Ryoichi in the feature Pacific Rim: Uprising (2018) and his lead role in the racing action movie Over Drive (2018). Mackenyu was cast as the villain, Enishi Yukishiro, in the blockbuster Rurouni Kenshin: Final Chapter (2021) and then as Scar in Fullmetal Alchemist: The Revenge Of Scar and Fullmetal Alchemist: Final Transmutation (2022).

In 2021, Mackenyu was cast as Roronoa Zoro in the Netflix live action series adaptation of One Piece (2023), and as the lead, Seiya, in the feature Knights of the Zodiac (2023). Mackenyu also stars in two Disney+ projects in 2023, the original live action/ anime mixed feature, Dragons of Wonderhatch and the drama series, House Of The Owl.