Called the Imaginarium, the space will be used to host talks, debates and lectures during the Festival of Imagination, which opens in the store on 16 January.
The installation will feature a circular "amphitheatre" contained within a polycarbonate wall. Other walls in the space will be clad in mirrors while the floor will be painted in an Op Art-style pattern of black and white stripes, which will be applied using a road-painting machine.
"We asked Rem [Koolhaas of OMA] to do it and he said yes," said Carlotta Jacoby, senior visual project manager at Selfridges. "It's quite a simple design but with the mirrored walls it's going to be pretty bonkers".
The stepped amphitheatre will seat up to 72 people. OMA has also designed the furniture for the space and a folding screen that will be used during talks. Columns will be painted with green-screen paint.
The Imaginarium will host daily events during the Festival of Imagination - a store-wide festival that will "explore the nature, power and positive impact of imagination". It will occupy the Ultralounge in the basement of the store, which is located on Oxford Street in central London.
The festival also features the Imagine Shop, a pop-up store curated by Dezeen that will showcase future-facing products and will contain an augmented reality watch store and an augmented reality model of a yacht designed by Zaha Hadid.
Sign up for a daily roundup
of all our stories