Conflans-Sainte-Honorine (French pronunciation: [kɔ̃flɑ̃ sɛ̃t ɔnɔʁin] ⓘ) is a commune in the Yvelines department in the Île-de-France region in north-central France.

The commune was originally named for its geographic position at the confluence of the Seine and Oise rivers.

Partly on account of its strategic position, Conflans-Sainte-Honorine is considered the capital of the French inland waterways, and the right bank of the river Seine is still lined with barges (although these are now used mainly as houseboats).

Every year in June, the town celebrates the Pardon national de la batellerie in remembrance of its former importance to inland shipping.

[6] Samuel Paty, a middle school teacher at Collège du Bois d'Aulne in Conflans-Sainte-Honorine, was killed and beheaded in 2020 in an Islamist terrorist attack.