Kaiō Hiroyuki, Japanese sumo wrestler
Kaiō Hiroyuki (born 24 July 1972 as Hiroyuki Koga) is a former professional sumo wrestler from Nōgata, Fukuoka, Japan.

He made his debut in 1988, reaching the top makuuchi division in 1993. He held the second highest rank of ōzeki or champion for eleven years from 2000 to 2011, and is the longest-serving ōzeki of all time in terms of number of tournaments fought.

In his career, Kaiō won five top division yūshō or tournament championships, the last coming in 2004. This is the modern record for someone who has not ultimately made the top rank of yokozuna. He was a runner-up in eleven other tournaments, and also won 15 sanshō or special prizes, the third highest ever.

In November 2009 he broke the record previously held by Takamiyama for the most tournaments ranked in the top division, and in January 2010 he surpassed Chiyonofuji's record of most top division bouts won. In the May 2010 tournament he became the only wrestler besides Chiyonofuji to reach one thousand career wins, and he surpassed Chiyonofuji's career wins record of 1045 in July 2011. He retired in the same tournament to become a coach at Tomozuna stable under the elder name Asakayama. In 2014, he established the latest incarnation of the Asakayama stable.