WWE.com has an article up on the top 10 youngest champions in WWE history.
The list includes:
No. 10 – Paige
The night after Wrestlemania 30 on RAW, Paige defeated AJ Lee for the WWE Diva’s championship. Paige was 21 years and 7 months.
No. 9 – Rey Mysterio
In the summer of 1996, Rey Mysterio defeated Dean Malenko to win the WCW Cruiserweight Championship on WCW Monday Nitro. Rey Mysterio was 21 years and 6 months.
No. 8 – 1-2-3 Kid (Sean Waltman)
1-2-3 Kid and former intercontinental champion Marty Jannetty defeated the Quebecers in early 1994 to become the WWE tag team champions. Sean Waltman was 21 years and 5 months.
No. 7 – Essa Rios
In February of 2000, On an episode of WWE Sunday Night Heat, Essa Rio accepted Gillberg’s open challenge for the Light Heavyweight title. Essa Rios defeated Gillberg to become the youngest Light Heavyweight Champion at 21 years and 2 months.
No. 6 – Hornswoggle
In 2007 at The Great American Bash, Hornswoggle won the Cruiserweight Championship Open. Wrestlers that competed in the match: Jimmy Wang Yang, Shannon Moore, Funaki, Jamie Noble and defending champion Chavo Guerrero. Hornswoggle was 21 years and 1 month.
No. 5 – David Flair
In 1999, David Flair was awarded the vacant WCW United States Championship by his father Ric Flair, who was the “WCW President” in the storyline. David Flair was 20 years and 3 months.
No. 4 – Kenny Dykstra
Kenny was a member of The Spirit Squad, team with Mickey and defeated the Big Show and Kane to capture the WWE World Tag Team Titles. Kenny was 20 years old.
No. 3 – Tyler Bate
Tyler won the WWE United Kingdom Championship Tournament by defeating Tucker, Jordan Devlin, the towering Wolfgang and the Bruiserweight. He wrestled four men in a span of two days to win it all. Tyler Bate was 19 years and 10 months.
No. 2 – René Duprée
In June of 2003, René Duprée and Sylvain Grenier, known as La Resistance won the WWE World Tag Team Championships. La Resistance defeated Kane and Rob Van Dam. René was 19 years and 6 months.
No. 1 – Nicholas
At WrestleMania 34, Braun Strowman needed a tag team partner in order to compete against Sheamus and Cesaro. Strowman “randomly” picked a little kid from the crowd. Strowman single handedly defeated The Bar to win the WWE RAW Tag Team championships. This made Nicholas the youngest person to ever hold any WWE title belt. Nicholas is said to be 10 years old.