The 19-year-old, a former West Ham trainee, played 15 times for Ipswich in the Championship last season.
Emmanuel made his professional debut in August 2015, 10 days before his 18th birthday, and later that season had a brief loan spell with Crawley.
He is the second Ipswich player to be signed on loan by Rotherham this week, after striker Kieffer Moore.
In total, Emmanuel has made 24 appearances for Ipswich.
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Rotherham United have signed Ipswich Town full-back Josh Emmanuel on a season-long loan deal.