The announcement was made at Rome noon or 6 a.m. eastern time Tuesday.
Knestout, who was most recently the Auxiliary Bishop of the Archdiocese of Washington, succeeds Bishop Francis X. DiLorenzo.
DiLorenzo passed away in August.
The Diocese of Richmond will celebrate Reverend Knestout with a Mass of Installation on January 12.
"A lot of it's going to be drinking from the fire hose and learning a lot," Knestout said of his goals when he is installed. "I know and recognize that there are some different aspects of this diocese. One is that a large number of colleges and universities within the diocese."
Knestout mentioned the need for unity and compassion throughout the 33,000 sq miles of diocese area that spans from Shenandoah Valley through Central, Southwest, Southside VA, east to Chesapeake Bay & Atlantic Ocean.
"There's lots of work to do in great missionary field in terms of the proclamation of the good news of the gospel to the people of this local church," he said.
Other church leaders called Tuesday an historic day and described the announcement as an early Christmas present for local Catholics.
Knestout, 55, was born and raised in Maryland.
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