Mariko Iwadate (岩館真理子, Iwadate Mariko, born 8 February 1957 in Sapporo, Hokkaidō, Japan)^[1] is a Japanese manga artist.

She made her debut as a manga artist in 1973 with the short story "Rakudai Shimasu" in the shōjo manga magazine Margaret. She then primarily wrote for the magazines Margaret and Young You.^[1][2]

She is considered one of the main artists of a movement in 1970s shōjo manga called otomechikku, alongside Ako Mutsu, Yumiko Tabuchi and Hideko Tachikake. Narratives in this movement focused more on everyday life situations, romances and psychological growth of Japanese high schools girls as opposed to the narratives of the Year 24 Group, which experimented with fantasy, science fiction and boys love often in international settings. Rachel Thorn describes that otomechikku manga "were heavily infused with a dreamy, 1970s-style femininity characterized by frilly cotton dresses, straw sun bonnets, herbal tea, and Victorian houses."^[3] Masanao Amano describes these early works as "stereotypical shoujo manga stories that were of very good quality".^[2]

By the 1980s, her works started exploring deeper themes. The short story "Angel", published in 1982, is marked as a stylistic turning point. In the story, the main character has an arranged marriage and ends up falling in love with her husband. Many of her manga focus on family relationships.^[2]

Natsume Fusanosuke explains that Iwadate uses white space boldly to suggest emotion and experiments with panel layouts to suggest an uncertainty in the frame.^[4]

Her work had an influence on writer Banana Yoshimoto. Amano describes Iwadate's work as "the combination of literature with shoujo manga".^[2][5]

She won the 1992 Kodansha Manga Award for shōjo for Uchi no Mama ga iu Koto ni wa,^[6] and her manga Ichigatsu ni wa Christmas ("Christmas in January") was adapted as an anime OVA in 1991.