Guy de Pourtalès (4 August 1881 Berlin – 12 June 1941 Lausanne) was a Swiss author.
He was the son of Herman Alexander de Pourtalès (1847–1904) and his first wife, Marguerite "Daisy" Marcet (1857–1888). Guy was born in Berlin, where his father at that time was an officer in the service of the Prussian king Wilhelm I. When he was six years old, the family returned to Switzerland, where they lived first at Malagny near Versoix in the Canton of Geneva and then, after his father's second marriage (with Hélène Barbey) in 1891, at Mies in the Canton de Vaud. Guy de Pourtalès went to schools in Geneva and in Vevey and then to the gymnasium in Neuchâtel. After his matura in 1899, he studied in Germany. In Karlsruhe, he began to study Chemistry, which he abandoned soon in favor of musical studies, which he continued from 1902 to 1905 at the University of Bonn. In 1905, he moved to Paris, where he studied literature at the Sorbonne.
Guy de Pourtalès published his first novel in Paris in 1910. One year later, he married Hélène Marcuard, with whom he had three children, and in 1912, his French nationality was restored upon his demand, since his family were Huguenots who had fled from France to Neuchâtel after the Edict of Fontainebleau revoking the Edict of Nantes. Just before World War I, his second novel appeared.
In 1914, he was drafted into service in the French army as a translator for the British troops in Flanders. At Ypres, he was gassed in 1915 and evacuated to Paris where he slowly recovered. He co-founded the Société littéraire de France, where he also published in 1917 his Deux contes de fées pour les grandes personnes ("Two fairy tales for grown-ups"). At the end of the war, he again served as a translator, this time for the American troops. After he was diagnosed with pulmonary tuberculosis in 1919, he rented the castle of Etoy in the Canton of Vaud in Switzerland in 1921 and henceforth would spend several months a year there. A large part of his literary work was written in Etoy.