The Lord High Executioner of Titipu in Gilbert and Sullivan's masterpiece The Mikado. Ko-Ko is usually played by a baritone. He is generally considered the male lead in this operetta, and while he sings during almost every song, his only true solos are "I've Got a Little List" and "On a Tree By a River."

At the beginning of the operetta, Ko-Ko has been condemned to death for flirting, but the Mikado releases him and makes him the Lord High Executioner. His ward Yum-Yum is to be his bride, but she is in love with Nanki-Poo, the Mikado's son, who is in turn lusted after by a noblewoman named Katisha. After the entire cast attempts multiple times to sort out their mangled love lives, Ko-Ko finds love with Katisha, and they sing their famed duet, "There is Beauty in the Bellow of the Blast."