He chose the Wildcats over Kansas, Illinois, Michigan State and Marquette.
"It was kind of pointless to continue to keep dragging it out longer."
Kentucky coach John Calipari was in Chicago on Monday to see Matthews work out, prompting speculation that he would become a Wildcat.
"I saw a lot of people thinking that (on social media) but we didn't even talk about me committing," Matthews said. "He was just here really letting me know to keep playing hard and continue to get better, really just showing support. Committing wasn't even part of the talk, I just felt that was the place I wanted to be."
The 6-foot-5 Matthews is rated the No. 15 player in the junior class by Scout and the No. 40 player in Scout's Ultimate 100. He comes from the same Meanstreets AAU program that produced former UK standout Anthony Davis and 2014 Wildcat signee Tyler Ulis.
"I spoke to Tyler. That's my man, so we talk a lot," Matthews said. "... We had a lot of fun this most recent summer with Meanstreets. Looking forward to continuing that."
Scout national basketball analyst Evan Daniels said Matthews is a "very good athlete and a true combo who plays well with the ball in his hands." He also predicted the long Matthews could become a very good defender at the next level.
Some UK fans may see some glimpses of former Wildcat DeAndre Liggins, another Chicago product, in Matthews' versatile play.
"Charles is a versatile and athletic guard who is capable of doing a lot of things on both ends of the floor," added Scout national basketball analyst Brian Snow. "He is tremendous in the mid-range and is a capable secondary ball handler who can slide to the point guard for short stretches. The upside with Matthews is huge."
Matthews is the 22nd five-star prospect in the Scout rankings to sign or commit to Kentucky since John Calipari arrived in Lexington in 2009. The UK boss has had at least one five-star prospect in each of his last six signing classes.
CLICK HERE to read more about Matthews's game in this junior primer by Scout national basketball analyst Rob Harrington.
CLICK HERE to watch highlights of Matthews in action.