Le Poizat-Lalleyriat () is a commune in the Ain department of eastern France. The municipality was established on 1 January 2016 and consists of the former communes of Lalleyriat and Le Poizat.
Le Poizat-Lalleyriat has an oceanic climate (Köppen climate classification Cfb). The average annual temperature in Le Poizat-Lalleyriat is . The average annual rainfall is with December as the wettest month. The temperatures are highest on average in July, at around , and lowest in January, at around . The highest temperature ever recorded in Le Poizat-Lalleyriat was on 31 July 1983; the coldest temperature ever recorded was on 9 January 1985.