Lalleyriat () is a former commune in the Ain department in eastern France. On 1 January 2016, it was merged into the new commune Le Poizat-Lalleyriat.
Lalleyriat has an oceanic climate (Köppen climate classification Cfb). The average annual temperature in 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 Lalleyriat was on 31 July 1983; the coldest temperature ever recorded was on 9 January 1985.