Rosemary Monica Wanjiru (born 9 December 1994)[1] is a Kenyan professional female long-distance runner.

Rosemary Wanjiru moved to Japan as a teenager and began competing in long-distance competitions there.

[5] The year after she was beaten into second place at the Japan Corporate Championships by another Kenyan, Ann Karindi Mwangi.

[2] At the World Championships she teamed up with compatriots Agnes Jebet Tirop and Hellen Obiri to lead the pace.

[8][9] In March 2023, Wanjiru won the Tokyo Marathon with a 2:16:28 clocking, taking more than a minute and a half off her personal best to move up to sixth on the event's world all-time list.