Alex de Minaur was unable to prevent Alexander Zverev from becoming the first man in nearly a decade to win consecutive titles at the Citi Open.
Top seed Zverev hit six aces, topping 210 km/h and never faced a break point en route to a 6-2 6-4 final victory to clinch his ninth career ATP title and third of 2018.
"You really deserved it," de Minaur told Zverev during the trophy ceremony.
"Played too good today."
Zverev improved to 16-2 for his career at Washington's tune-up for the US Open, which commences in three weeks.
Juan Martin del Potro won the Washington event in 2008 and 2009.
Germany's Zverev is 21, and Australia's de Minaur is 19, making for the youngest final on the ATP World Tour since 20-year-old Rafael Nadal beat 19-year-old Novak Djokovic at Indian Wells in 2007.
"I'm sure these kind of trophies will be in your hands very soon," Zverev told de Minaur.
Even though Sunday's hard-court tournament finalists are close in age, Zverev held quite an advantage in size and experience.
He is 6-foot-6, ranked No.3 and one of only five active players with at least three Masters titles (the others are Nadal, Djokovic, Roger Federer and Andy Murray).
De Minaur is 5-foot-11, projected to be 45th when the latest rankings are releases and yet to win a tour-level title of any sort.
Zverev put on a dominant performance on a steamy afternoon.
The sun was a contrast to all of the rain during the week that jumbled the schedule and led to Andy Murray's withdrawal for a quarter-final against de Minaur.
Zverev broke de Minaur's serve in the opening game and again to lead 4-0 after all of 15 minutes, while they would go on to play for another full hour, the outcome seemed rather clear from that moment.
Zverev's serve was unbreable while he generated 11 break point chances on the de Minaur serve and converted three of them.
Zverev's booming groundstrokes were often too much to handle for de Minaur, whose body language often told the tale of how things were going.