Barty lost the match 1-6, 6-3, 6-2 as Muchova continued taking down higher ranked opponents. She had earlier beaten her compatriot and world No.1 6 Karolina Pliskova before beating 18th ranked Elise Mertens of Belgium in the fourth round.
The 19-year-old ensured her place in history as Poland's first major singles champion on Saturday, becoming the ninth woman in 14 tournaments to secure her maiden Slam title