Boulter became the 11th British singles player to fall at the first hurdle at Wimbledon after losing to 6-2 6-4 to Italian teenager Tyra Caterina Grant.
It is the first time since 2017 that Boulter has lost in the opening round at Wimbledon, with this her first-ever loss to a qualifier at a Grand Slam tournament.
It comes just 18 days after she achieved the biggest win of her career by ranking, when she defeated world number two Elena Rybakina in a stunning performance at Queen’s.
Seeking to push back against unwanted history on court three, Boulter got off to the worst possible start as Grant, who had never contested a singles match on grass at any level prior to Wimbledon qualifying this year, went an early break up.
Boulter could not respond as the opening set slipped away and she was unable to recover from another setback early in the second.
The Briton did not force a single break point in the match, with Grant dropping just three points across her final four service games as she comfortably served out victory.
The 18-year-old Grant was making her Grand Slam main-draw debut after coming through qualifying.
Last year, 13 British players went out in round one. Not since 1988 have as many as 16 fallen at the first hurdle.
A total of nine British players are in action on day two at the All England Club.
Also on Tuesday, Jack Pinnington Jones returns to complete his match against American 28th seed Brandon Nakashima, trailing 6-3, 7-6(5), 4-3.
Eastbourne semi-finalist Toby Samuel faces 15th seed Jakub Mensik, while British number two Jan Choinski takes on Vit Kopriva.
Jacob Fearnley meets American Alex Michelsen, Arthur Fery faces Damir Dzumhur, Billy Harris is up against 19th seed Karen Khachanov, and Harry Wendelken comes up against Valentin Royer.
