Chieftain of the Germanic Cherusci. Segimer or Sigimer (Latin: Segimerus or Sigimerus) was a chieftain of the Germanic Cherusci and the father of Arminius and through Flavus the grandfather of Italicus.

Segimer was at first an ally of Rome. Both of his sons, Arminius and Flavus, entered the Roman military. According to Cassius Dio, Segimer was the second-in-command of Arminius during the latter’s rebellion against the Romans, which in 9 AD culminated a crushing Roman defeat at the Battle of the Teutoburg Forest. Flavus, however, remained loyal to Rome. During Germanicus' campaigns against Arminius, Segimer, unlike his brother Inguiomer, is not mentioned by Tacitus as having participated.