Katsuyuki Sakai

 is a Japanese rugby union player. He plays for the Japanese club Toyota Industries Shuttles in the Top League. He also plays rugby sevens for Japan's national rugby sevens team and was named in their 2016 Summer Olympics squad.
He captained the Japanese squad when they played at the 2014 Hong Kong Sevens and won the World Series Qualifier for the 2014–15 Sevens World Series. He was also a member of the squad that won the 2015 ARFU Men's Sevens Championships to qualify for the 2016 Summer Olympics.