MEDOACUS or MEDUACUS(Μεδόακος: Brenta), a river of Northern Italy, in the province of Venetia, falling into the extensive lagunes which border the coast of the Adriatic, in the neighbourhood of the modern Venice. According to Pliny (Plin. Nat. 3.16. s. 20), there were two rivers of the name, but no other author mentions more than one, and Livy, a native of the region, mentions the Meduacus amniswithout any distinctive epithet. (Liv. 10.2.) There can be no doubt that this is the river now known as the Brenta, which is a very considerable stream, rising in the mountains of the Val Sugana, and flowing near Padua(Patavium). A short distance from that city it receives the waters of the Bacchiglione, which may probably be the other branch of the Medoacus meant by Pliny. Strabo speaks of a port of the same name at its mouth (Μεδόακος λιμήν, 5. p. 213), which served as the port of Patavium. This must evidently be the same to which Pliny gives the name of Portus Edro, and which was formed by the Medoaci duo ac Fossa Clodia :it is in all probability the one now called Porto di Lido, close to Venice. The changes which have taken place in the configuration of the lagunes and the channels of the rivers, which are now wholly artificial, render the identification of the ports along this coast very obscure, but Strabo's statement that the Medoacus was navigated for a distance of 250 stadia, from the port at its mouth to Patavium, seems conclusive in favour of the Porto di Lido, rather than the more distant one of Chiozza. At the present day the Brentaflows, as it were, round the lagunes, and enters the sea at Brondolo, evidently the Portus Brundulus of Pliny (l. c.) ; while a canal called the Canale di Brenta, quitting the river of that name at Dolo, holds a more direct course to the lagunes at Fusina. This canal may perhaps be the Fossa Clodia of Pliny.
Livy tells us that, in B.C. 301, Cleonymus the Lacedaemonian arrived at the mouth of the Medoacus, and having ascended the riverwith some of his lighter vessels, began to ravage the territory of the Patavini, but that people repulsed his attacks, and destroyed a considerable part of his fleet. (Liv. 10.2.)
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