Yvelines (French: [ivlin] ⓘ eev-leen) is a department in the western part of the Île-de-France region in Northern France.

[6] Yvelines is bordered by the departments of Val-d'Oise on the north, Hauts-de-Seine on the east, Essonne on the southeast, Eure-et-Loir on the southwest and Eure on the west.

Besides Versailles (the prefecture and most populous commune) and the subprefectures of Mantes-la-Jolie, Rambouillet, and Saint-Germain-en-Laye, important cities include Conflans-Sainte-Honorine, Poissy, Les Mureaux, Houilles, Plaisir, Sartrouville, Chatou, Le Chesnay, and the new agglomeration community of Saint-Quentin-en-Yvelines.

In both local and national elections, the department generally supports centre-right political candidates.

Michel Rocard, who served as Prime Minister of France from 1988 to 1991 under President François Mitterrand, was an MP for the department in the Socialist Party.