“Trump won — Save America,” the banner, which was unfurled over the wall of the bleacher section in centerfield during the fourth inning, read. The Red Sox were playing a home game against the Miami Marlins.
The incident happened while the Marlins training staff was examining starting pitcher Zach Thompson before the start of the bottom of the fourth inning. Thompson threw some warm up pitches before exiting the game with an apparent injury.
The fan was promptly removed from the stadium by security, as the Red Sox have a rule forbidding signs from being hung or affixed to the ballpark.
It's unclear whether the fan will face any further punishment, such as a temporary ban from Red Sox games.
A request for comment on the matter has not yet been returned.
The incident comes after similar banners have been unfurled during Mets and Yankees games in recent weeks.
Two men attending a Yankees game last month were also escorted from the ballpark after unveiling their banner.
Images of the banner were shared across social media by others present at the game and among Trump fans.
"Trump Won Fenway," wrote user Dion Cini who posted a video of the sign.
"In Boston the players, staff and fans were all cheering for Trump," he claimed.
The banners are referencing claims from Trump that the 2020 election was a “big lie” and riddled with fraud, which has sparked some states to launch audits of the election.
“The 2020 Election, which didn’t even have Legislative approvals from many States (which is required under the U.S. Constitution), and was also otherwise corrupt, was indeed The Big Lie,” Trump declared in a message on May 6. “An even greater Hoax than Russia, Russia, Russia, Mueller, Mueller, Mueller, Impeachment Hoax #1, Impeachment Hoax #2, or any of the other many scams the Democrats pulled!”
No evidence has been found to support the claims and dozens of lawsuits in a number of states have been tossed out because of the lack of supporting evidence.
Reactions to the banner seen on Monday night's game were mixed online.
"Guys, we need to cut this out [or] they're going to bring back the pandemic," user @adamberaha joked.
"By this logic, did Hilary Clinton win in 2016 too?" hit back another.
This is not the first time a sign has stirred controversy at Fenway park.
In 2017, four fans were ejected for holding a banner reading: "Racism is as American and baseball."
Similar to the Fenway incident, the individuals involved in the stunt were escorted out of the ball game in the fourth inning.