Marketa Vondrousova's Wimbledon title defence came to an early end as she fell to a surprise first-round defeat by Spain's Jessica Bouzas Maneiro.
The Czech became the first unseeded player to win the women's singles trophy when she triumphed against Ons Jabeur in last year's final.
But Vondrousova's game was riddled with unforced errors and double faults as the 25-year-old opened proceedings with a lacklustre performance on Centre Court.
World number 83 Bouzas Maneiro, 21, took advantage on Tuesday to win 6-4 6-2 for her first Grand Slam victory.
"I am really happy, I think this is one of the most important moments in my life, in my career," said Bouzas Maneiro.