The Cavaliers (14-3) have won three straight league crowns and four of the past five.
The first 10 minutes of the opening half was a back-and-forth game between the tournament's top two seeds, who were tied at 2.
Kelly Kasper's goal gave the Terrapins a 3-2 advantage at 19:28, and Maryland went on a four-goal run over the next 14 minutes.
Virginia cut the lead to 5-3 on a goal by McCulloch during the Maryland run but trailed 7-3 at halftime.
The Terps (15-2) built an 8-3 lead early in the second half before the Cavaliers went on a 6-0 run.
Virginia's Kaitlin Duff scored on a free position play with 21:27 left to start the run. With the Terps trailing 9-8, Caitlyn McFadden (Notre Dame Prep) scored with 1:58 left to force overtime.
Dana Dobbie led Maryland with three goals and also had an assist.
McCulloch, Brittany Kalkstein (Roland Park) and Kaitlin Swagart each had two goals for the Cavaliers, and McCulloch had a pair of assists.
Terps goalie Allie Buote and the Cavaliers' Kendall McBrearty each made eight saves.
No. 5 Pennsylvania 11, No. 1 Northwestern 7 -- Hilary Bowen and Meredith Frank each had a hat trick as the host Quakers (13-1) upset the Wildcats (15-1) and ruined their bid for a perfect season. The loss ended a program-best 36-game winning streak. Northwestern led 7-5 at halftime before Penn went on a 6-0 run and outshot the Wildcats 10-4 in the second half. Sarah Waxman finished with seven saves for Penn, and Morgan Lathrop had six for Northwestern.
No. 1 Duke 11, No. 3 Virginia 9 -- Dan Loftus recorded a season-high 17 saves to help the Blue Devils (15-1) repeat as ACC champions at Klockner Stadium in Charlottesville. Duke led 11-3 with six minutes left in the third period and held off a determined Cavaliers team during the last 21-plus minutes to win the program's sixth ACC title, including the second straight and the fourth in the past eight years. Duke has won five straight against the Cavaliers but trails in the all-time series 48-20. Duke beat Virginia in last year's ACC title match, 12-9. Matt Danowski led Duke with three goals. Brian Carroll (Gilman) and Ben Rubeor (Loyola) each had three goals for the Cavaliers.
No. 4 Notre Dame 17, No. 16 Ohio State 12 -- The host Fighting Irish (11-2, 4-1) - led by Michael Podgajny and Grant Krebs (St. Mary's) with three goals each - extended their home winning streak to 18 games and forced a three-way tie in the Great Western Lacrosse League. Notre Dame, Ohio State (9-4, 4-1) and Denver finished with 4-1 conference records. The Fighting Irish will be the No. 1 seed at next weekend's inaugural Great Western Lacrosse League tournament.