Pryor, a 6-foot-5 wing, had also considered Florida and Gonzaga.
"The history, the tradition, the brotherhood really stood out to me. Everything felt like it was a family," Pryor said. "They checked all the boxes I was looking for in a school and the need and want for me, and off the court having a Georgetown degree is second to none."
Pryor averaged 18.0 points and 8.0 rebounds last season for Robert Morris, earning first-team all-conference honors.
With leading scorer D'Vauntes Smith-Rivera playing his senior season in 2015-16, Georgetown badly needed some scoring punch on the perimeter.
"It was, to me and my family, the best decision towards my ultimate goal, which is to play in the NBA," Pryor said.
Pryor joins four-star recruit Jagan Mosley and junior college transfer Jonathan Mulmore as players entering the Georgetown program next fall.