Étienne Constantin, Baron de Gerlache (French pronunciation: [etjɛn kɔ̃stɑ̃tɛ̃ baʁɔ̃ də ʒɛʁlaʃ]; 26 December 1785 – 10 February 1871) was a lawyer and politician in the United Kingdom of the Netherlands, and later became in 1831 the first prime minister of the newly founded Belgian state.

He studied law in Paris and practised there for some time, but settled at Liège after the establishment of the kingdom of the Netherlands.

[5] On the outbreak of disturbance in August 1830 he still, however, thought the Orange-Nassau dynasty and the union with the Dutch states essential; but his views changed, and, after holding various offices in the provisional government, he became president of congress, and brought forward the motion inviting Leopold of Saxe-Coburg to become king of the Belgians.

That his early Liberal views underwent some modification is plain from the Conservative principles enunciated in his Essai sur le mouvement des partis en Belgique (Brussels, 1852).

His Histoire des Pays-Bas depuis 1814 jusquen 1830 (Brussels, 2 vols., 1839), which reached a fourth edition in 1875, was a piece of special pleading against the Dutch domination.