The pop icon will perform extra shows in London, Birmingham and Blackpool due to phenomenal public demand.
The singer will now perform three nights at the O2 between August 24 and August 26.
Tickets for the new shows will be available from Ticketmaster from 10am on February 13.
The full list of UK and Ireland shows is below.
August 17 - Scarborough, Open air theatre
August 18 - Manchester Arena
August 20 - Dublin, Ireland 3Arena
August 22 - Glasgow, SSE Hydro
August 24 - London, the O2
August 25 - London, the O2
August 26 - London, the O2
August 31 - Birmingham, UK Genting Arena
September 1 - Blackpool, UK Tower Festival
It has also been revealed that Pitbull will join her as a support act as part of the European tour.
Britney will also visit Brighton Pride for a special performance on August 4 as part of the tour.
The shows follow Spears' successful Las Vegas residency, which she's held since 2013.