Rio Shirai

is a Japanese swimmer. She competed in the women's 4 × 100 metre freestyle relay event at the 2018 Asian Games, winning the gold medal.

As a 14-year-old at the 2014 Junior Pan Pacific Swimming Championships in Hawaii, United States, Shirai won the gold medal in the 200 metre backstroke with a 2:11.67, the bronze medal in the 100 metre backstroke with a 1:01.82, and a silver medal in the 4×100 metre medley relay with a final relay time of 4:04.11. The following edition, the 2016 Junior Pan Pacific Swimming Championships also held in Hawaii, United States, she won a bronze medal in the 4×200 metre freestyle relay, splitting a 1:59.88 for the fourth leg of the relay to help achieve a final time of 8:08.12.