Just Stop Oil protesters stopped an opera performance by setting off a confetti bomb and blasting an air horn.
Three activists jumped from their seats at Glyndebourne and started shouting.
The audience was watching Dialogues des Carmelites at the opera house in East Sussex.
Audience members booed and shouted: “Disgraceful!” before the three were removed from the auditorium.
The performance restarted 20 minutes later.
No arrests were made.
A spokesman for Glyndebourne said:
“We are very sorry to everyone whose visit was affected by the protest action.
“Our highest priority was the safety and security of everyone on site, and we would like to thank our staff and performers, whose calm and professional response kept everyone safe and disruption to a minimum.
“At approximately 5.31pm, today’s performance of Poulenc’s Dialogues des Carmelites was disrupted by three protesters who let off a confetti bomb, blew an air horn and started shouting.
“The stage was immediately cleared and within less than a minute ushers had peacefully escorted the protesters from the theatre.
“The audience remained inside the theatre and were provided with regular updates and, following a 21-minute delay, the opera restarted at approximately 5.52pm.
“We have formally reported the incident to the police, but the police were not on site and no arrests were made.”
