Lucius Munatius Plancus (c. 87 BC-c. 15 BC) was a Roman senator, consul in 42 BC, and censor in 22 BC with Aemilius Lepidus Paullus.

According to Suetonius, Plancus was the one who suggested Octavian adopt the title "Augustus" rather than be called Romulus as a "second founder of Rome" (Seut., Div. Aug. 7). His early career is rather unclear. Few things are known about him. He was Julius Caesar's officer during the conquest of Gaul and the civil war against Gnaeus Pompeius Magnus. When Caesar was assassinated on March 15th, 44 BC, Plancus was the Proconsul of Gallia Comata. But in the next year he turned to Mark Antony, and he held the consulship with Marcus Aemilius Lepidus in the year of 42 BC. He became proconsul of Asia in about 40 BC. During Mark Antony's expedition to Armenia and Parthia, to avenge Crassus's death, he was the proconsul of Syria. But when Antony's campaign against the Parthians failed, he choose to leave him and join Octavian.

In the year 22 BC, Augustus appointed him and Aemilius Lepidus Paullus to fill the office of Censor (Suet. Aug. 37, Claud. 16; Dion Cass. liv.2). Their censorship is very famous not because of their remarkable deeds, but because it was the last time that such magistrates were appointed. According to C. Velleius Paterculus' Roman history, it was a shame for both of the senators: "...the censorship of Plancus and Paullus, which, exercised as it was with mutual discord, was little credit to themselves or little benefit to the state, for the one lacked the force, the other the character, in keeping with the office; Paullus was scarcely capable of filling the censor's office, while Plancus had only too much reason to fear it, nor was there any charge which he could make against young men, or hear others make, of which he, old though he was, could not recognize himself as guilty..." (Book II: Chapter 95).

We know the story from Suetonius' Life of Nero, chapter 4, that Emperor Nero's grandfather, Lucius Domitius Ahenobarbus, whose wife was Antonia Major, daughter of Mark Antony, "was haughty, extravagant, and cruel, and when he was only an aedile, forced the censor Lucius Plancus to make way for him on the street." This may be a symbol of the poor reputation Plancus held after his censorship.