A 110-seater studio theatre has opened in a former car park underneath the Menier Chocolate Factory in Southwark Street.
The theatre's inaugural season began on Wednesday with Skin a Cat, transferred from the VAULT Festival in Waterloo.
"The Bunker offers a chance for audiences to tell us what they want and what matters to them," said executive producer Joel Fisher.
"Being in the heart of Southwark in this incredible creative hub means that we can start to pinpoint who our audience are and what shows they want to be seeing.
"This part of London is quickly becoming a cultural hub with developments at Tate Modern and the Globe and the London Theatre Company taking up residency at One Tower Bridge, and The Bunker joins this cultural movement. We want to share ideas with the theatres around us and find new and exciting ways of collaborating.
Artistic director Joshua McTaggart said: "The Bunker isn't a place where you would leave straight after a show but rather a place that you could hang around in, meet the creatives involved and talk about the piece with your peers.
"In a way, it's about creating a community who want to discuss what they have seen and debate what it means to them.
"It is true that at this unpredictable financial time, opening a new theatre is going to be a risky venture but, as artists, we always approach risk with creativity and ambition.
"For us, this opportunity was about doing something and doing it differently.
"It has been a privilege to curate a first season that brings together some of the best emerging and established talent this country has to offer and to see our collaborators' enthusiasm and excitement for The Bunker proves that the stress and struggles have been worth it."