Gaius Appuleius Decianus was tribune of the plebs in 98 BC, known primarily for his connection to politically motivated prosecutions in the Late Roman Republic.
Decianus attempted to prosecute Publius Furius (tribune in 100 or 99 BC), but according to Cicero, lost the case because he expressed sorrow over the killing of the radical tribune Lucius Appuleius Saturninus. Decianus's commitment to popularist politics is well-established and consistent. His father was the Publius Decius (praetor 115 BC) who prosecuted Lucius Opimius for the murder of the popularist leader Gaius Gracchus. The formation of the name Appuleius Decianus indicates that he was adopted by a member of the gens Appuleia and perhaps even by Saturninus himself. "Tumultuous efforts" were made during the tribunate of Decianus to avenge the deaths of Saturninus and Servilius Glaucia.
The trial of Furius was politically motivated; no actual charge is even recorded, but may have been ambitus (election irregularities). Furius had originally supported Saturninus, but ultimately broke with him as did the majority of the tax-collecting equestrian order who rejected his plebs-friendly policies. Growing opposition to Saturninus had compelled Gaius Marius to renounce him, resulting in his proscription and death. Furius had proposed a number of post-mortem penalties, such as the confiscation of his property, the destruction of his house, and the rescinding of some of his legislation. The social conflicts that culminated in Saturninus's death continued to play out in the law courts during the 90s. Decianus brought the case against Furius in retaliation, and chose to present it for the judgment of the people (iudicium populi) rather than in the court for which equites acted as judges.