Keely Hodgkinson added a world 800m silver medal to her Olympic silver from last summer after an epic battle between the Briton and the United States' Athing Mu.
Mu and Hodgkinson, both 20 years old, won gold and silver medals respectively in Tokyo last year, and it was the same result in Eugene, Oregon, as the U.S. star took the world title.
But Hodgkinson pushed Mu all the way and finished just eight-hundredths of a second behind the home favourite, who won in a time of 1:56.30.
Hodgkinson crossed the finish line in a time of 1:56.38, while Kenya's Mary Moraa won bronze with a personal best of 1:56.71.
Hodgkinson admitted to being disappointed with silver given she had thought she could pass Mu in the last 100m.
But she also expressed excitement at future contests with Mu.
"I went to the inside, but the gap wasn't there," Hodgkinson said.
"I ran to the line, gave it everything and I am happy with world silver.
"I got so close, but it is what it is and I am proud to have given myself a chance out there.
"Athing is a great athlete. We are both 20 and have many years ahead of us and we'll meet on a world podium again."
Meanwhile, Great Britain's 4x400m women's relay team claimed bronze to wrap up the country's seventh and final medal in Oregon.
Laviai Nielsen, Nicole Yeargin, Victoria Ohuruogu and Jessie Knight finished behind the U.S. and Jamaica on the podium, with the Americans winning their third successive world title.
It capped a world championships in which Britain claimed one gold medal, one silver medal and five bronze medals, finishing 11th in the overall table.
Information from Reuters was included in this article.