The British Rail Class 55, also known as a Deltic, or English Electric Type 5, is a class of diesel locomotive built in 1961 and 1962 by English Electric for British Railways. Twenty-two locomotives were built, designed for the high-speed express passenger services on the East Coast Main Line (ECML) between Edinburgh and London King's Cross. They gained the name "Deltic" from the prototype locomotive, DP1 Deltic, which in turn was named after its Napier Deltic power units.

The English Electric Company Limited (EE) was a British industrial manufacturer formed after the armistice ending the fighting of World War I by amalgamating five businesses which, during the war, had been making munitions, armaments and aeroplanes.