From literal French, In Search of Lost Time, first translated into English as Remembrance of Things Past, and sometimes referred to in French as La Recherche (The Search), is a novel in seven volumes by French author Marcel Proust. This early 20th-century work is his most prominent, known both for its length and its theme of involuntary memory. The most famous example is the "episode of the madeleine," which occurs early in the first volume. The novel gained fame in English in translations by C. K. Scott Moncrieff and Terence Kilmartin as Remembrance of Things Past.

In Search of Lost Time follows the narrator's recollections of childhood and experiences into adulthood in the late 19th-century and early 20th-century high-society France while reflecting on the loss of time and lack of meaning in the world. The novel began to take shape in 1909. Proust continued to work on it until his final illness in 1922 forced him to break off. Proust established the structure early on, but even after volumes were initially finished, he continued to add new material and edited one volume after another for publication. The last three of the seven volumes contain oversights and fragmentary or unpolished passages, as they existed only in draft form at the author's death; the publication of these parts was overseen by his brother Robert.