愚人节也称万愚节、幽默节，愚人节节期为公历4月1日，是从19世纪开始在西方兴起流行的民间节日，并未被任何国家认定为法定节日。在这一天人们以各种方式互相欺骗和捉弄，往往在玩笑的最后才揭穿并宣告捉弄对象为“愚人”。玩笑的性质极少包含实质恶意，但个别玩笑由于开得过大而引起人们的恐慌，产生较大规模反响及衍生成为（传媒）谣言和都市传说，所以对于人们来说一般会加以避免如灾难之事的玩笑。
AprilFool'sDayisalsocalled"AprilFool'sDay"and"humorousFestival".ThefoolisgraduallyontheGregoriancalendar.InApril1st,itbeganinnineteenthCenturyandbecameapopularfolkfestivalintheWest.Ithasnotbeenrecognizedasalegalholidaybyanycountry.Onthisday,peoplecheatandmakefunofeachotherinvariousways,oftenattheendofjokesonlytoexposeandmakefunof"fools".Thenatureofthejokerarelycontainssubstantialmalicious,butindividualjokebecauseoftoomuchopeningcausedpanic,producelargerrepercussionsandbecome(media)rumorsandurbanlegends,soforpeoplewillgenerallybeavoidedifdisasterthatjoke.