 St Kilda ( Scottish Gaelic : Hiort ) is an isolated archipelago 64 kilometres ( 40 mi ) west @-@ northwest of North Uist in the North Atlantic Ocean . It contains the westernmost islands of the Outer Hebrides of Scotland . The largest island is Hirta , whose sea cliffs are the highest in the United Kingdom ; three other islands ( Dùn , Soay and Boreray ) were also used for grazing and seabird hunting . The islands are administratively a part of the Comhairle nan Eilean Siar local authority area . 
