The Basilica of Neptune (Latin: basilica Neptuni) was a basilica built in Rome by Marcus Vipsanius Agrippa in honour of Neptune and in celebration of his naval victories at Mylae, Naulochus and Actium.

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Basilica of Neptune

Remains of its decoration, including marine elements.
Basilica of Neptune Shown within Augustan Rome
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Coordinates	41°53′53.76″N 12°28′37.39″E

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Near the site of the Pantheon, its remains were restored under Hadrian for an unknown use. The Temple of Hadrian was once misidentified with the basilica.^[1]

It was part of building works on the Campus Martius between 33 and 25 BC, possibly financed by the proceeds of Octavian's campaign in Illyria between 35 and 33 BC. The project also included the Pantheon, the Saepta Iulia and the Baths of Agrippa.

The structure of the Basilica of Neptune is much more similar to the central halls of the imperial baths than to the classic Roman civil basilicas, resembling the 4th century Basilica of Maxentius. The construction, in brick, and the style date back to the Hadrianic period, but the basilica reaches the early Augustan period.