Lang, of the United States, collected four birdies in the final eight holes to card an impressive five-under-par 67, while Sweden’s Sophie Gustafson – who won this event at Royal Birkdale in 2000, before it gained major status – was third on 11 under.
Amy Yang of South Korea was fourth, a further shot back.
While Tseng became the first woman to defend the title since America’s Sherri Steinhauer in 1999, Masson was left to reflect on a heartbreaking last day as her dreams of glory vanished in a flurry of bogeys.
They came at the second, third, seventh, 10th, 11th and 15th holes, while a double bogey at the par-four 12 had her slumping to eight over for the round, though she climbed back up the leaderboard with birdies on the last two holes.
Tseng, who earned a first prize of £239047, said: “It feels really good. I played so consistently today and I enjoyed the crowd here.
