Gaius Dillius Luci filius Auli nepos Sergia Aponianus was soldier of ancient Rome, of Spanish origin. He replaced Titus Aurelius Fulvus and joined Marcus Antonius Primus as legate of the Legio III Gallica in the year 69-70.
His men refused to swear allegiance to Vitellius during the Year of the Four Emperors, instead favoring Vespasian. Aponianus does not appear to have been aligned with any of the four emperors, aside from being under Vitellius at the time, and he asked the governor of Moesia—his relative Marcus Aponius Saturninus—for assistance. Saturninus informed Vitellius of the legion's refusal, but not that their allegiance was aligned with Vespasian. Legio III Gallica went on to be instrumental in inflaming legionary sentiment against Vitellius (and for Vespasian), and in the Second Battle of Bedriacum, where they fought for Vespasian.
Aponianus is believed to have served as a suffect consul some time around 71 or 73. His name appears as consul in literary sources, but not the Fasti consulares, so it is difficult to fix the exact year. Paul Gillivan suggests the possible dates for his tenure as suffect consul could be November/December 71, the last half of 72, or March/April of 73. However, more recently Giuseppi Camodeca has completed the list of consuls for 71, so the available dates for his tenure are now limited to 72 and 73.
There is epigraphical evidence of him being responsible for repairs made on the right bank of the Tiber River in 73.