thumb|Contemporary effigy of Prince Sicard, namesake of the Pactum, from one of his coins
The Pactum Sicardi was a treaty signed on 4 July 836 between the Greek Duchy of Naples, including its satellite city-states of Sorrento and Amalfi, represented by Bishop John IV and Duke Andrew II, and the Lombard Prince of Benevento, Sicard. The treaty was an armistice ending a war between the Greek states and Benevento, during which the Byzantine Empire had not intervened on behalf of its subjects. It was supposed to last five years.

By the treaty Prince Sicard recognised the rights of merchants from the three cities to travel through his domains. He made navigation up the rivers Patria, Volturno, and Minturno open to merchants, responsales (envoys), and milities (soldiers). Sicard did not give up his powers of enforcement over either the illegal slave trade (in Lombards) or the trafficking in stolen merchandise. He did abolish the lex naufragii (law of shipwreck) by which the landowner on whose shores a wrecked ship or its cargo washed up was the possessor of that wealth: "If a ship is wrecked because of the fault [of the men aboard] the goods found in it are to be returned to the one to whome they belonged and still belong." This measure, protecting the property rights of shipping companies and merchants, was "far in advance of thes times".

Despite these efforts, a war began again in 837, when Duke Andrew of Naples called in Saracens as allies against Benevento. In 838 Sicard captured Amalfi by sea.