The lex Titia was a Roman law passed on 27 November 43 BC, that legalised the Second Triumvirate of Octavian, Mark Antony, and Marcus Aemilius Lepidus for a period of five years. The triumvirate established by the law was renewed in 38 BC. Unlike the First Triumvirate, which was a private arrangement between three men, this was a legal instrument which vested the three men with dictatorial powers.
The Second Triumvirate, nominally a "three-man commission for restoring the constitution of the republic" (triumviri rei publicae constituendae) was given the power to make or annul laws without the need for approval from the Senate or the people, insulated their judicial decisions from appeal, allowed the Triumvirs to name magistrates at will, and manage state lands. Although the three members possessed the full powers of their office, unlike the the normal republican magistracies, the triumvirs could not veto one another.
While the constitutional machinery of the republic was not dismantled by the lex Titia, it never recovered, and over the next two decades, would transform into the constitution of the Roman Empire. Certainly, it can be argued that in Roman constitutional theory, the law's passage was simply an exercise of the sovereign people's legislative authority. The passing of the lex Titia marked the de jure end of the Roman Republic,[dubious ] though in practice it had already been repeatedly subverted by prior legislation, such as that which conferred dictatorships on past generals, such as Sulla and Julius Caesar.