thumb|right|300px|Map of the [[Roman Empire in AD 125, under emperor Hadrian, showing the Legio I Adiutrix, stationed on the river Danube at Brigetio (Szőny, Hungary), in Pannonia Superior province, from AD 86 to at least 344]]
thumb|300px|I Adiutrix celebrated by [[Septimius Severus with this denarius. I Adiutrix supported Severus in his fight for the purple.]]
thumb|Brick stamp LEG I AD found in [[Rheinzabern.]]
Legio I Adiutrix ( First Legion "Rescuer"), was a legion of the Imperial Roman army founded in AD 68, probably by Nero or Galba when he rebelled against emperor Nero (r. 54–68). The last record mentioning the Adiutrix is in 344, when it was stationed at Brigetio (modern Szőny), in the Roman province of Pannonia. The emblem of the legion was a capricorn, used along with the winged horse Pegasus, on the helmets the symbol used by I Adiutrix legionaries was a dolphin. Tacitus mentions that marines Nero had brought into Rome were still present in the city when Galba arrived from Spain; both Suetonius and Dio Cassius state that Galba created the legion. H.M.D. Parker argues that the dies natalis, or official date of creation when it received its aquila standard, of the legion was 22 December 68.
Year of the Four Emperors
In the confusing Year of the Four Emperors, the legion fought in Otho's army in the Battle of Bedriacum, where this emperor was defeated by Vitellius The victorious Vitellius ordered the legion transferred to Spain, but by the year 70 it was fighting in the Batavian rebellion.
thumb|Helmet of Lucius Lucretius Celer, Soldier in the centuria of Gaius Mummius Lolianus of the Legio I Adiutrix
Stationed in Moguntiacum
The city of Moguntiacum (Mainz) is the legion's first known base camp, shared with Legio XIV Gemina, where they attended mainly building activities. In 83, they fought the Germanic wars against the Chatti, a German tribe living across the Rhine, under the command of Emperor Domitian. After that they were transferred to the Danubian army stationed in the Roman province of Pannonia, to fight the Dacians.
Legio I Adiutrix Pia Fidelis
Following the murder of Domitian in 96, the Adiutrix, along with the Danubian army, played an important role in Roman politics, forcing Nerva to adopt Trajan as his successor. When Trajan became emperor, he gave the legion the cognomen Pia Fidelis ("loyal and faithful") to acknowledge their support. Between 101 and 106, under the new emperor's command, I Adiutrix, along with IV Flavia Felix and XIII Gemina, conquered Dacia and occupied the newly formed province. Trajan also used his Pia Fidelis in the campaign against Parthia (115–117), but they were sent back to Pannonia by his successor emperor Hadrian, with base in Brigetio.
| legatus legionis
| c. 134 - c. 137
| Pannonia Superior
|
|-
| Titus Flavius Longinus
| legatus legionis
| c. 143-c. 146
| Pannonia Superior
| IGRR I, 622
|-
| Gaius Julius Commodus Orfitianus
| legatus legionis
| c. 193
| Pannonia Superior
|
|-
| Gaius Junius Faustinus Placidus Postumianus