Ryuji Ishii (石井 龍司, Ishii Ryūji, born Fukuoka, 13 March 1970) is a Japanese former rugby union player. He played as flanker.

At club level, Ishii played throughout all of his career for Toyota Verblitz until his retirement. His only cap for Japan was against Spain, in Tokyo, on 20 August 1999. He was called up to play in the 1999 Rugby World Cup squad, but he never played any match in the tournament. Between 2004 and 2010, Ishi was appointed as manager for Toyota Verblitz.^[2]

• Ryuji Ishii at ESPNscrum