Mori Ranmaru (森 蘭丸?, 1565 – June 21, 1582), also known as Mori Naritoshi (森 成利), was the son of Mori Yoshinari, and had 5 brothers in total, from the province of Mino. He was a member of the Mori Clan, descendants of the Seiwa Genji.
From an early age, Ranmaru was an attendant to Oda Nobunaga. Recognized for his talent, loyalty, and unusual beauty, he was appointed to a responsible post. At Ōmi, he was given 500 koku, and after Takeda Katsuyori's death, he was awarded the 50,000 koku at Iwamura Castle. Ranmaru and his younger brothers perished defending Oda Nobunaga during the Honnō-ji Incident. Ranmaru's bravery and devotion is remembered throughout history, and especially during the Edo period because of his decision to commit seppuku and follow Nobunaga in death.
Oda and Mori's lord-vassal relationship was thought to have followed the nanshoku tradition - an intimate relationship - and was widely admired in Japan for its strength. In nanshoku literature of the Edo period, it was widely understood that Oda and Mori had a sexual relationship that was commonly found in those times.
Ranmaru has often been the subject of works of art since the Edo period, and continues to be seen in various forms of modern fictional media today. Due to admiration for his loyalty, Ranmaru has been depicted as a loyal page of Nobunaga in various works of classical Japanese art. Such works include ukiyo-e prints by artists such as Kuniyoshi, Yoshitoshi, and Toshihide. He has also been a character in kabuki plays such as Tsuruya Namboku IV's Toki-ha Ima Kikyô no Hataage.