IER can refer to:
- Instance équité et réconciliation, a Moroccan human rights commission
- Institute of Education and Research
- International Economic Review, an economics journal
- Interurban Electric Railway, a division of the Southern Pacific Railroad in the U.S.
- Institute for Energy Research, a nonprofit public policy think tank
- New South Wales Institute for Educational Research, an Australian educational research institute
- Individual Electoral Registration, a reform of electoral registration in the United Kingdom proposed by the Coalition Government
- IER (company), a subsidiary of the Bollore group which owns Source London and electric car charging infrastructure
The Ier or Eriu is a right tributary of the river Barcău (Berettyó) in Romania and Hungary. It discharges into the Barcău in Pocsaj. The Andrid Dam is constructed on this river. The Ier flows through the villages Mihăieni, Eriu-Sâncrai, Ghirolt, Rădulești, Hotoan, Sudurău, Dindești, Andrid, Sălacea, Cherechiu, Săcueni, Diosig in Romania, and Pocsaj in Hungary.