A flashmob is a group of people that quickly assemble in a public place and do something strange or unexpected for a short amount of time, then disperse rapidly.

The first flash mob was created in Manhattan in May 2003, by Bill Wasik, senior editor of Harper's Magazine. The origins of the flash mobs were unknown until Wasik published an article about his creation in the March 2006 edition of Harper's. The first attempt was unsuccessful after the targeted retail store was tipped off about the plan for people to gather. Wasik avoided such problems during the second flash mob, which occurred on June 3, 2003 at Macy's department store, by sending participants to preliminary staging areas—in four prearranged Manhattan bars—where they received further instructions about the ultimate event and location just before the event began.