| Ryūki Watarai | |
| Position: | Outfielder |
| Team: | Yokohama DeNA BayStars |
| Number: | 4 |
| Bats: | Left |
| Throws: | Right |
| Birth Date: | 4 October 2002 |
| Birth Place: | Ichikawa, Chiba, Japan |
| Debutdate: | March 29 |
| Debutyear: | 2024 |
| Debutteam: | Yokohama DeNA BayStars |
| Debutleague: | NPB |
| Statyear: | July 21, 2024 |
| Statleague: | NPB |
| Stat1label: | Batting average |
| Stat1value: | .261 |
| Stat2label: | Hits |
| Stat2value: | 60 |
| Stat3label: | Home runs |
| Stat3value: | 3 |
| Stat4label: | RBI |
| Stat4value: | 24 |
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| Awards: | |
is a Japanese professional baseball outfielder for the Yokohama DeNA BayStars of Nippon Professional Baseball (NPB).
His father is Hirobumi Watarai, a former professional baseball player for the Tokyo Yakult Swallows.