Live performances, where groups of people collectively experience dance, music, or theatre, are a ubiquitous feature of human cultures. Yet, neuroscientific studies of these inherently social art forms almost exclusively involve people watching video or sound recordings alone in a laboratory. Across three live dance performances, we simultaneously measured real-time dynamics between the brains of up to 23 audience members using mobile wet-electrode EEG. Inter-brain synchrony (IBS) in the delta band (1-4 Hz) varied systematically with the dancers’ movements and the audiences’ collective engagement as predicted by the choreographer. IBS was reduced when people watched a video of the performance on their own in a laboratory. Choreographic sections with higher IBS were also rated as more engaging by an independent sample of viewers. Our study shows that live experiences are measurable as dynamic brain synchrony between co-present spectators and reflects artistically directed collective engagement with a live dance performance.