As far as I'm aware - the youngest Champion of a Challenger Tour event was Michael Chang when he won a Challenger event in Las Vegas in 1987 when he was 15 years and 7 months old. Not that surprising considering he also won the French Open at 17.

From what I remember hearing also - Richard Gasquet was pretty young when he started winning Futures and Challengers as well - while he was 16 I think.

I'll try to find some sources to back up my claims and come back here and edit this answer afterwards.

Two sources found by Martin (in the comments)

1. http://www.menstennisforums.com/showthread.php?t=239122

2. http://www.atpworldtour.com/News/Tennis/2014/07/28/Challenger-Weekly-Spotlight-7-July-2014.aspx

As far as I'm aware - the youngest Champion of a Challenger Tour event was Michael Chang when he won a Challenger event in Las Vegas in 1987 when he was 15 years and 7 months old. Not that surprising considering he also won the French Open at 17.

From what I remember hearing also - Richard Gasquet was pretty young when he started winning Futures and Challengers as well - while he was 16 I think.

I'll try to find some sources to back up my claims and come back here and edit this answer afterwards.

Two sources found by Martin (in the comments)

1. http://www.menstennisforums.com/showthread.php?t=239122

2. http://www.atpworldtour.com/News/Tennis/2014/07/28/Challenger-Weekly-Spotlight-7-July-2014.aspx (snapshot in Wayback machine)

As far as I'm aware - the youngest Champion of a Challenger Tour event was Michael Chang when he won a Challenger event in Las Vegas in 1987 when he was 15 years and 7 months old. Not that surprising considering he also won the French Open at 17.

From what I remember hearing also - Richard Gasquet was pretty young when he started winning Futures and Challengers as well - while he was 16 I think.

I'll try to find some sources to back up my claims and come back here and edit this answer afterwards.

As far as I'm aware - the youngest Champion of a Challenger Tour event was Michael Chang when he won a Challenger event in Las Vegas in 1987 when he was 15 years and 7 months old. Not that surprising considering he also won the French Open at 17.

From what I remember hearing also - Richard Gasquet was pretty young when he started winning Futures and Challengers as well - while he was 16 I think.

I'll try to find some sources to back up my claims and come back here and edit this answer afterwards.

Two sources found by Martin (in the comments)

1. http://www.menstennisforums.com/showthread.php?t=239122

2. http://www.atpworldtour.com/News/Tennis/2014/07/28/Challenger-Weekly-Spotlight-7-July-2014.aspx