- Birth Name: Yokoyama Reina (横山玲奈)
- Nickname: Yokoyan (よこやん)
- Date of Birth: February 22, 2001
- Place of Birth: Saitama, Japan
- Blood Type: O
- Height: 152cm
- Specialty: Playing various instruments, alto sax, jazz dance
- Hobbies: Listening to music, dancing, singing
- Looks Up To: Oda Sakura, Hirose Ayaka
- Hello! Project groups:
Yokoyama Reina first appeared as a member of Hello Pro Kenshuusei through an announcement on the official Hello! Project website on August 17, 2016. She later made her first public appearance at the "Hello! Project Kenshuusei Happyoukai 2016 9gatsu ~SINGING!~" event on September 4th. Prior to joining she was a participant in the first Morning Musume 13th Generation Shinseiki Audition that resulted in no winners.
After the lack of finalists in the first run and second re-run of the Morning Musume 13th Generation audition, it was announced that the winners would be chosen from the Hello Pro Kenshuusei. Yokoyama was revealed as one of two winners of the Morning Musume 13th Generation Shinseiki Audition on December 12, 2016, alongside fellow Hello Pro Kenshuusei member Kaga Kaede, in an announcement at Nippon Budokan during the last performance of the Morning Musume fall tour.
- [2018.07.04] First REINA YOKOYAMA
- [2018.06.27] THIS IS REINA
- [2019.08.27] REINA is eighteen~N to S~
- TV Programs
- [2016–] Hello! Station (ハロ！ステ)
-  Reversible Radio (リバーシブルラジオ) (fan club exclusive)
-  Hello Pro no Oshigoto Challenge! (ハロプロのお仕事チャレンジ!)
- [2017–] Morning Musume '17 no Morning Diary (モーニング娘。'17のモーニングダイアリー)
- [2017–] marukome Morning Misoshiru Nomou yo! (marukome モーニングみそ汁 飲もうよ!)
- [2017–] Young Town Doyoubi (ヤングタウン土曜日)
- Her official Morning Musume image color is golden yellow.
- Considers her charm points to be her bangs, eyes, sneeze, and loud laugh.
- Her favorite genre of music is J-Pop.
- Her favorite sports are dance and soccer.
- Her motto is "Use time wisely!"
- Favorite foods are shougayaki and spring rolls.
- Her favorite Hello! Project songs are "Osu! Kobushi Damashii" by Kobushi Factory and "The Vision" and "Souda! We're ALIVE" by Morning Musume.
- Can play several instruments including alto sax, acoustic guitar, and piano.
- Learned to play piano at home.
- Participated in brass instruments clubs or bands in both elementary and middle school, where she played percussion and sax respectively.
- Competed in the 62nd All Japan Band Competition in 2014 using her alto sax.
- Loves history and eventually wants to become a certified UNESCO World Heritage Site expert.