Marlieux (; ) is a commune in the Ain department in eastern France. MarlieuxâÂÂChâtillon station has rail connections to Bourg-en-Bresse and Lyon.
The river Chalaronne forms part of the commune's western border.
Marlieux has an oceanic climate (Köppen climate classification Cfb). The average annual temperature in Marlieux is . The average annual rainfall is with October 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 Marlieux was on 13 August 2003; the coldest temperature ever recorded was on 6 January 1971.