'''ヨーロッパの五月祭'''(ヨーロッパのごがつさい、メーデー('''May Day'''))とは、古代ローマの祭に由来する祭。5月1日に、豊穣の女神[[マイア]]を祭り供物が捧げられた。また、ヨーロッパに古くから伝わる夏の始まりを祝うお祭りで、通常、春分と夏至の中間の5月1日に祝われる。夏の豊穣を予祝する祭りと考えられている。現在では、ヨーロッパ各地で、キリスト教伝来以前にさかのぼる起源をもつ、春の訪れを祝う日として定着している。英語ではthe May Festival、May dayなどと呼ぶ<ref>[http://dictionary.goo.ne.jp/leaf/je2/25559/m0u/%E4%BA%94%E6%9C%88%E7%A5%AD/ goo辞書]</ref><ref name="Melton">Melton J. Gordon, Religious Celebrations, ABC-CLIO, 2011 , isbn:9781598842050, page915</ref><ref>May Day Celebrations, https://www.historic-uk.com/CultureUK/May-Day-Celebrations/, 2021-05-02, Historic UK</ref>。
また、前日の夜には「メイ・イブ('''May Eve''')」と呼ばれるお祭りが行われることもあります。伝統では野草や緑の枝を集め、花輪を編み、メイクイーン(May Queen)を戴き(男性の伴侶を伴うこともある)、メイポール、メイツリー、メイブッシュ<ref group="私注">これらは冬の象徴である植物神で、倒されねばならないものであるように感じる。</ref>を設置し、その周りで人々が踊るという伝統的なものである。を設置し、その周りで人々が踊るという伝統的なものである<ref>May Day, https://www.britannica.com/topic/May-Day-European-seasonal-holiday, July 26, 2016, Encyclopaedia Britannica|pub, Encyclopaedia Britannica, inc., The Editors of Encyclopaedia Britannica</ref>。また、地域によっては焚き火(Bonfire)をするところもある。
'''May Day''' is a European festival of ancient origins marking the beginning of summer, usually celebrated on [[1 May]], around halfway between the [[March equinox|spring equinox]] and [[summer solstice]]. Festivities may also be held the night before, known as '''May Eve'''. Traditions often include gathering wildflowers and green branches, weaving floral [[garland]]s, crowning a [[May Queen]] (sometimes with a [[Jack in the Green|male companion]]), and setting up a [[Maypole]], May Tree or May Bush, around which people dance.<ref>{{Cite web|title=May Day|url=https://www.britannica.com/topic/May-Day-European-seasonal-holiday|date=July 26, 2016|website=Encyclopaedia Britannica|publisher=Encyclopaedia Britannica, inc.|others=The Editors of Encyclopaedia Britannica}}</ref> [[Bonfire]]s are also part of the festival in some regions. Regional varieties and related traditions include [[Walpurgis Night]] in central and northern Europe,<ref name="Melton"/> the [[Gaels|Gaelic]] festival [[Beltane]],<ref name="Hutton Beltane">{{Cite book |last=Hutton |first=Ronald |title=Stations of the Sun: A History of the Ritual Year in Britain |date=1996 |publisher=[[Oxford University Press]] |isbn=978-0-19-820570-8 |pages=218–225 |author-link=Ronald Hutton}}</ref> the [[Wales|Welsh]] festival [[Calan Mai]],<ref name="Hutton Beltane"/> and [[May devotions to the Blessed Virgin Mary]]. It has also been associated with the [[Religion in ancient Rome|ancient Roman]] festival [[Floralia]].<ref>{{cite book |last1=Joshua |first1=Essaka |title=The Romantics and the May Day Tradition |date=2016 |publisher=[[Routledge]] |page=16}}</ref>
In 1889, 1 May was chosen as the date for [[International Workers' Day]] by the [[Second International]], to commemorate the [[Haymarket affair]] in [[Chicago]] and the struggle for an eight-hour working day.<ref name="Foner">{{Cite book |last=Foner |first=Philip S. |url=https://archive.org/details/maydayshorthisto0000fone |title=May Day: A Short History of the International Workers' Holiday, 1886–1986 |publisher=International Publishers |year=1986 |isbn=0-7178-0624-3 |location=New York |pages=[https://archive.org/details/maydayshorthisto0000fone/page/41 41–43] |author-link=Philip S. Foner |url-access=registration}}</ref> As a result, International Workers' Day is also called "May Day", but the two are otherwise unrelated.