
John Brett1831–1902Britannia's Realm is an oil on canvas landscape painting by the British artist John Brett, from 1880. It is held at the Tate Britain, in London.
A seascape, it features a view of the Carmarthen Bay near Tenby, in Pembrokeshire. Brett was one of the best-known landscape painters associated with the Pre-Raphaelite Brotherhood. He often produced views of British coastal scenes.
The painting was displayed at the Royal Academy Exhibition of 1880 held at Burlington House. Today it is in the collection of the Tate Britain, having been acquired the same year as part of the Chantrey Bequest for £600.