The lex Vatinia (probably passed in May or early June 59 BC)[1][2][3] also known as the lex Vatinia de provincia Caesaris[4] or the lex Vatinia de imperio Caesaris,[5] was legislation which gave Gaius Julius Caesar governorship of the provinces of Cisalpine Gaul and Illyricum for five years.[6][7][3] It was named after and proposed, in the Tribal Assembly, by plebeian tribune Publius Vatinius.[8] Along with the provinces, it also gave him the three legions already present there and the privilege of naming his own legates.[9] Caesar also received Titus Labienus as legatus cum imperio in the law; Labienus' appointment may have been, according to Syme, a sign of friendship between Pompey and Caesar.[10]
Caesar seemed to want to use the law to prepare for a war of choice against the kingdom of Dacia.[11] However, after the unexpected death of the governor of Transalpine Gaul, and at the proposal of Pompey and Piso,[6] the senate also added to Caesar's assigned provinces the further Gaul as well, giving him another legion.[8] According to Cicero and Suetonius, the senate's assignment was done out of fear that if they did not do so, a tribune would introduce and the people would pass further legislation assigning the province as well.[12]