J'ouvert ( joo-VAY) or Jour ouvert is a traditional festival known as "break day" or the unofficial start of Carnival, which takes place on the Monday before Ash Wednesday. The festival, with origins in Trinidad, traditionally begins at 2 a.m. and continues until mid-morning on Monday. J'Ouvert revellers cover their bodies in coloured paints, mud, pitch oil, dress as blue or red devils to dance the streets as an expression of liberation from the constraints of the past and in celebration of the ancestors who have gone before them. Other neighbouring islands (primarily in the Lesser Antilles), and in areas where Caribbean people have immigrated, celebrate J'ouvert before the official start of Carnival Mas, where the more elaborate costumes are on display and danced through the city streets.

J'ouvert is a gallicization of jou ouvè (IPA: [ʒu uvɛ]; jour ouvert in standard French), the French Creole term meaning "dawn" or "daybreak", as this is the time at which the celebration is typically held.