The 6-foot, 185-pound Diggs, who is Scout.com's No. 2 receiver in the 2012 class, announced minutes ago he was heading to Maryland.
"I want to win championships and what's a better place to do it than in your city?" Diggs said in making his selection.
It gives the Terps a strong finish to a class in which their last three commitments were Diggs and four-star running backs Albert Reid and Wes Brown, a teammate of Diggs at Our Lady of Good Counsel in Olney, Md.
He chose the Terps over Ohio State, Auburn, Florida and Virginia, and should be an immediate asset in the offense.
"Diggs lines up all over the field for his Good Counsel team, but he does most of his damage from a running back position," Scout.com director of scouting Scott Kennedy said. "He has feet that would make a sewing machine envious, capable of making the quickest of cuts in traffic. He has excellent vision and good top-end speed.
"When spread outside at receiver, he shows enough ability to be there full-time if that's where he's needed. He's a a natural with the ball in his hands."
FoxSportsNext/Scout.com's Kristen Kenney contributed to this report and will have full coverage of Diggs' decision