Collective memory is the shared pool of memories, knowledge and information of a social group that is significantly associated with the group's identity. The English phrase "collective memory" and the equivalent French phrase "la mémoire collective" appeared in the second half of the nineteenth century. The philosopher and sociologist Maurice Halbwachs analyzed and advanced the concept of the collective memory in the book Les cadres sociaux de la mémoire (1925).

Collective memory can be constructed, shared, and passed on by large and small social groups. Examples of these groups can include nations, generations, communities, among others.

Collective memory has been a topic of interest and research across a number of disciplines, including psychology, sociology, history, philosophy, and anthropology.

Collective memory has been conceptualized in several ways and proposed to have certain attributes. For instance, collective memory can refer to a shared body of knowledge (e.g., memory of a nation's past leaders or presidents); the image, narrative, values and ideas of a social group; or the continuous process by which collective memories of events change.

The difference between history and collective memory is best understood when comparing the aims and characteristics of each. A goal of history broadly is to provide a comprehensive, accurate, and unbiased portrayal of past events. This often includes the representation and comparison of multiple perspectives and the integration of these perspectives and details to provide a complete and accurate account. In contrast, collective memory focuses on a single perspective, for instance, the perspective of one social group, nation, or community. Consequently, collective memory represents past events as associated with the values, narratives and biases specific to that group.

Studies have found that people from different nations can have major differences in their recollections of the past. In one study where American and Russian students were instructed to recall significant events from World War II and these lists of events were compared, the majority of events recalled by the American and Russian students were not shared. Differences in the events recalled and emotional views towards the Civil War, World War II and the Iraq War have also been found in a study comparing collective memory between generations of Americans.

The concept of collective memory, initially developed by Halbwachs, has been explored and expanded from various angles – a few of these are introduced below.

James E. Young has introduced the notion of 'collected memory' (opposed to collective memory), marking memory's inherently fragmented, collected and individual character, while Jan Assmann develops the notion of 'communicative memory', a variety of collective memory based on everyday communication. This form of memory resembles the exchanges in oral cultures or the memories collected (and made collective) through oral tradition. As another subform of collective memories, Assmann mentions forms detached from the everyday; they can be particular materialized and fixed points as, e.g. texts and monuments.