Legio III Italica was a Roman legion levied by Marcus Aurelius around 165, for his campaign against the Marcomanni tribe. The cognomen Italica suggests that recruits were originally from Italy. The legion was still active in Germania in the later 4th century. The legion's symbol was a stork.
Together with legions II Italica and I Adiutrix, III Italica legion was in the Danube provinces from its beginning, fighting the invasion of the Raetia and Noricum provinces by the Marcomanni. In 171 they built the camp Regina Castra, modern Regensburg, designed as a strongly defensive position like a castle.
In the civil war of 193, this legion supported Lucius Septimius Severus and helped him defeat his opponents first Pertinax and Didius Julianus, then Pescennius Niger and Clodius Albinus. Their loyalty was extended to Severus' successor, emperor Caracalla, for whom they fought in 213 a campaign against the Alamanni.
As a part of the powerful Danubian army, III Italica took part in the frequent struggles for internal power in the 3rd century. Their main camp was still Regensburg, but they were included in the 273 campaign commanded by emperor Aurelian against queen Zenobia.
The legion is still mentioned by the sources in the late 4th century in the Danubian provinces.
See also: List of Roman legions
livius.org account of Legio III Italica (http://www.livius.org/le-lh/legio/iii_italica.html)