the acts of union 1800 (or sometimes acts of union 1801) (irish: "acht an aontais 1800") is used to describe two acts are meant. their official titles are the union with ireland act 1800 (1800 c.67 39 and 40 geo 3), an act of the parliament of great britain, and the act of union (ireland) 1800 (1800 c.38 40 geo 3), an act of the parliament of ireland.