The Temple of Apollo Sosianus is a Roman temple dedicated to Apollo in the Campus Martius, next to the Theatre of Marcellus and the Porticus Octaviae, in Rome, Italy. Its present name derives from that of its final rebuilder, Gaius Sosius.
The three columns of the temple which survive to full-height today belong to the Augustan rebuild, but the cult of Apollo had existed in this area since at least to the mid-5th century BC when an Apollinar (a sacred grove or altar) was recorded on this site. Since Apollo was a foreign cult, it thus legally had to be placed outside the pomerium, making it a regular spot for extra-pomerial senate meetings.
