Sir Susantha de Fonseka KBE (25 April 1900 – 1 January 1963) was a Ceylonese statesman and diplomat.

Upon his return to Ceylon, he became the principal of Sri Sumangala College, Panadura, after which he went on to become the editor of The Morning Leader.

This was brought to the attention of Admiral Sir Geoffrey Layton, Commander-in-Chief, Ceylon who saw it as an act of disloyalty by a naval officer, specially since the speech was made while in uniform, had De Fonseka, commission withdrawn.

Susantha de Fonseka as the State Council member for Panadura, moved a motion in the State Council, by November 1944, to the effect that the Ministers "be directed to introduce immediately a Bill conferring on this country a constitution of the recognized dominion type for Free Lanka".

[7] Ambassador de Fonseka built up such close contacts with the Burmese leadership that he was associated with Prime Minister U Na when Karen guerrillas surrendered.

de Fonseka and the uncle and godfather to popular cinema icon Tissa Abeysekara, whose father was also Susantha's cousin.