| Ryuji Horii | |
| Fullname: | Ryuji Horii |
| Strokes: | Backstroke |
| Birth Date: | 25 November 1974 |
| Birth Place: | Osaka, Japan |
| Weight: | 68kg (150lb) |
is a retired Japanese male backstroke swimmer. He represented Japan at the 1996 Summer Olympics in Atlanta, Georgia. He is best known for winning a silver medal at the 1995 Summer Universiade in Fukuoka.