Hannah Rankin (5-3) failed in her bid to win the IBF, WBA and WBC middleweight titles, losing on points to American Claressa Shields (7-0) in Kansas.
The 28-year-old Glaswegian was aiming to become the first female boxer from Scotland to ever win a world title, despite being a huge underdog, but Shields won by unanimous decision to retain her unbeaten record.
All three judges at the Kansas Star Arena and Casino scored the 10-round fight 100-90.
Rankin, originally from Luss, held her own in the opening round but was rocked by a right hook in the second segment as Shields began to show her superior quality.
Shields continued to dominate with the jab, and again landed a heavy right in the seventh.
A dogged Rankin, trained by Noel Callan, rallied in the ninth but had to withstand a heavy barrage in the final round as her opponent looked to end the one-seided fight with a knockout.
The 23-year-old from Michigan took every round on the sorecards in the third defence of her IBF and WBA straps and added the WBC belt to her collection. The Flint fighter has been a titleholder since her second pro fight in March 2017, just four months after her pro debut.
The WBC Silver female middleweight champion from Scotland has now lost her last two World championship fights.