The Rat Pack was a group of actors originally centered on Humphrey Bogart. In the mid-1960s it was the name used by the press and the general public to refer to a later variation of the group, after Bogart's death, that called itself "the summit" or "the clan," featuring Frank Sinatra, Dean Martin, Sammy Davis, Jr., Peter Lawford, and Joey Bishop, who appeared together on stage and in films in the early-1960s, including the movie Ocean's Eleven.

For a brief stint, the 1960s version of the group also included Norman Fell. Marilyn Monroe, Angie Dickinson, Juliet Prowse, and Shirley MacLaine were often referred to as the "Rat Pack Mascots", a title which reportedly made these ladies feel like "one of the boys". The post-Bogart version of the group (Bogart died in 1957) was reportedly never called that name by any of its members — they called it the Summit or the Clan. "The Rat Pack" was a term used by journalists and outsiders, although it remains the lasting name for the group.

Often, when one of the members was scheduled to give a performance, the rest of the Pack would show up for an impromptu show, causing much excitement among audiences, resulting in return visits. They sold out almost all of their appearances, and people would come pouring into Las Vegas, sometimes sleeping in cars and hotel lobbies when they could not find rooms, just to be part of the Rat Pack entertainment experience. The marquees of the hotels at which they were performing as individuals would read, for example, "DEAN MARTIN - MAYBE FRANK - MAYBE SAMMY" as seen on a Sands Hotel sign.