Kitagawa Rio was born on March 16, 2004 in Tokyo, Japan.
On June 22, she was announced as a winner of the Morning Musume '19 LOVE Audition and would join Morning Musume '19 as a 15th generation member alongside Okamura Homare and Yamazaki Mei. They were introduced on stage during the Hello! Project 2019 SUMMER concert tour from July 13 and will begin performing with the group in the Morning Musume '19 Concert Tour Aki.
On August 28, Kitagawa, Okamura, and Yamazaki held their debut fanclub event, Morning Musume '19 15ki Member FC Event, at Yamano Hall.
On September 5, the 15th generation members began a fanclub-exclusive web talk show, titled Three stations.
On March 25, she was scheduled to celebrate her 16th birthday at a fanclub event titled Morning Musume '20 Kitagawa Rio Birthday Event, featuring two shows at LANDMARK HALL. However, it was cancelled in consideration of a new policy established by the government to prevent the spread of COVID-19. It was later rescheduled.
On March 16, Kitagawa celebrated her 17th birthday at a fanclub event titled Morning Musume '21 Kitagawa Rio Birthday Event, featuring two shows at KT Zepp Yokohama in Yokohama.
On March 23, Kitagawa celebrated her 18th birthday at a fanclub event titled Morning Musume '22 Kitagawa Rio Birthday Event, featuring two shows at Katsushika Symphony Hills Mozart Hall in Tokyo.
When Kitagawa joined Morning Musume, she was in her last year of middle school, she graduated middle school and began high school on following April. On March 20, 2022, Kitagawa announced she graduated high school. On June 24, 2022, it was revealed via a web interview with Ray Magazine that Kitagawa had started attending university in Spring 2022. 
A list of nicknames that have been used to refer to Kitagawa Rio:
- Kitario (きたりお): Her nickname as a member of Morning Musume.
- Rio (りお): A nickname she wrote on her Morning Musume '19 LOVE Audition application.
- Mizunomi Babaa (水飲みババア; Water-Drinking Granny): A nickname given to Kitagawa by her classmates, which she wrote on her Morning Musume '19 LOVE Audition application. On a school sports day, she had muscle pain and wasn't feeling well, so she collected and drank all the extra water that no one else wanted. Because her classmates thought she was like an old woman, they called her "Mizunomi Babaa".
- On-chan (おんちゃん): Used by fans.
- Name: Kitagawa Rio (北川莉央)
- Nickname: Kitario (きたりお)
- Birthdate: March 16, 2004
- Birthplace: Tokyo, Japan
- Blood Type: O
- Height: 155.4 cm (5 ft 1.1 in)?
- Western Zodiac: Pisces
- Eastern Zodiac: Monkey
- Hello! Project Status:
- 2019-06-22: Morning Musume member
- UP-FRONT PROMOTION Status:
- 2019-06-22: Member
- Morning Musume Member Color:
- Sea Blue
- Hello! Project Groups:
- Morning Musume (2019-present)
- Other Groups:
- Main article: Kitagawa Rio/Publications
- [2019–] Hello! Project Station
- [2019–] Upcoming
- [2019–] tiny tiny
- [2019–] OMAKE CHANNEL
-  Hello Pro Kouhaku Taiko THE☆BATTLE 2019
-  Hello Pro ONE×ONE
-  Hello Pro no Oshigoto Challenge! 2
-  Kimi ni Tsutaetai Monogatari
- [2019–] Morning Musume '19 no Morning Jogakuin ~Houkago Meeting~ (モーニング娘。'19のモーニング女学院〜放課後ミーティング〜)
- [2019–] Three stations (fanclub exclusive)
- She shares the same surname with former Hello Pro Kenshuusei Hokkaido member Kitagawa Ryo.
- She had been wanting to work in the entertainment industry for eight years before she joined Morning Musume.
- During her first interview as a member of Morning Musume, she stated her desire was to be able to keep up and perform well despite not having much experience.
- When she joined Morning Musume, she said she would like to sing Oda Sakura's solo part in "Help me!!". She also said in another interview that her favorite song is "Ai no Gundan" because it has a powerful dance and many noticeable singing parts.
- She is bad at sports, except for golfing. Her best golf score is 98 as of June 2019.
- She loves water. Her favorite water bottle brand is Volvic.
- She began supporting female idols in the fifth grade, when she started liking the K-pop group Girls' Generation (known as Shoujo Jidai in Japan).
- She is the third Morning Musume member to attend university while active in the group after Sato Masaki and Nonaka Miki.