Belgian media are reporting that Princess Marie-Esméralda was arrested in London earlier this week for her role in climate change protests.
According to Belgium newspaper Le Soir, the Princess was arrested in Trafalgar Square for her role in the Extinction Rebellion protests which brought much of London to a standstill.
She has been released from custody without charge.
More than 1,100 Extinction Rebellion protesters have been arrested since their week-long protests began on Monday.
They have caused travel chaos by blocking many major roads, as well as causing disruption at airports.
Princess Esméralda is the daughter of Leopold III, King of the Belgians from 1934 until 1951.
The 63-year-old is the half-sister of King Baudouin and King Albert II, and the aunt of the current King Philippe.
