Stanley was selected by the Ravens 6th overall in the first round of the 2016 NFL draft and earned Pro Bowl and first-team All-Pro honors in 2019.

He contemplated entering the 2015 NFL draft, but ultimately decided to return to Notre Dame for his senior season.

Head coach John Harbaugh named Stanley the starting left tackle to begin the regular season.

[16] He made his professional regular season debut and first career start in the Ravens' 13–7 victory against the Buffalo Bills.

[22] Head coach John Harbaugh retained Stanley as the starting left tackle to begin the regular season in 2018.

[24] Stanley continued his development blocking for quarterback Lamar Jackson and running backs Mark Ingram and Gus Edwards, which by week 15 broke Ravens scoring record set in 2014.

[25] On October 30, 2020, the Ravens signed Stanley to a five-year contract extension worth $112.8M in maximum total value,[26] making him the highest paid offensive lineman in the NFL.

On November 1, 2020, in a Week 8 game against the Pittsburgh Steelers, Stanley was carted off the field with a season-ending ankle injury.