Junko Saito (斉藤 淳子, Saitō Jun'ko) (née Nakajima (中島 淳子, Nakajima Jun'ko, born 2 May 1952), more commonly known by her stage name Mari Natsuki (夏木 マリ, Natsuki Mari), is a Japanese singer, dancer and actress.

In 2007, Natsuki announced her engagement to percussionist Nobu Saitō (斉藤ノヴ) , with their marriage taking place in Spring 2008.

Natsuki has participated in musical theatre, including Madame Thenardier in Les Miserables, Golde in Fiddler on the Roof and that of Yukio Ninagawa.

Natsuki played the character Big Mama in the Japanese version of Metal Gear Solid 4: Guns of the Patriots[2] and has also acted in television dramas, such as the 2005 series Nobuta o Produce, playing the Vice Principal, Katharine.

In 2024, Natsuki reprised her famous roles of Yubaba/Zeniba for the stage production of Spirited Away, performing in Japan and London.