American teenager Madison Keys beat German fifth seed Angelique Kerber 6-3 3-6 7-5 in the final of the Aegon International in Eastbourne.
It is the 19-year-old's first tournament victory on the WTA Tour.
Keys hit 60 winners and 17 aces against Kerber, who lost the 2012 Eastbourne final to Tamira Paszek after passing up five championship points.
In the men's final, defending champion Feliciano Lopez beat top seed Richard Gasquet 6-3 6-7 (5-7) 7-5.
Playing in her first final, the unseeded Keys is the first American to win the event since Chanda Rubin won back-to-back titles in 2002 and 2003.
She is the youngest American to win a singles event since Vania King triumphed in Bangkok in October 2006.
"It was a bit surreal playing in my first final but I tried to stay calm and not over-think it," said Keys, who will move into the world's top 30 ahead of Wimbledon, which starts on Monday.
"Hopefully there will be many more [titles] to come."
Keys struck one serve clocked at 126mph, the fastest this year on the WTA Tour and one of the top-five fastest since records began in 1989.
Kerber, who also reached the semi-finals at Wimbledon in 2012, has now lost three finals this year after defeats in Sydney and Doha.
In the men's final, two breaks helped world number 25 Lopez secure the first set, only for Frenchman Gasquet to draw level by winning a second-set tie-break.
In the deciding set, Spaniard Lopez broke to lead 6-5 and then held his serve to win the fourth title of his career.