Austin, 54, finished with an 11-under total for three rounds at The Country Club of Virginia's James River Course. He won his fourth senior title and first since 2016.
Langer, 61, the defending tournament champion and season points leader, birdied the final hole for a 70. The winner last week in North Carolina, the German closed the front nine with consecutive birdies, but he had several birdie putts slide on the back.
Haas, 64, the second-round leader after a 65, had a 74 to tie for third with Fran Quinn (69) and Kent Jones (70) at 9 under. Haas was bidding to become the oldest winner in the history of the tour for players 50 and older.
The top 72 players qualified for the Charles Schwab Cup Playoffs opener. The top 54 move on to the Invesco QQQ Championship next week in Thousand Oaks, California, and the top 36 after that will advance to the season-ending Charles Schwab Cup Championship in Phoenix.