Fidenae was an ancient town of Latium, situated about 5 miles north of Rome on the Via Salaria, which ran between it and the Tiber.

It was for some while the frontier of the Roman territory and was often in the hands of Veii. It appears to have fallen under the Roman sway after the capture of this town, and is spoken of by classical authors as a place almost deserted in their time. It seems, however; to have had some importance as a post station. The site of the arx of the ancient town is probably to be sought on the hill on which lies the Villa Spada, though no traces of early buildings or defences are to be seen: pre-Roman tombs are to be found in the cliffs to the north.

The later village lay at the foot of the hill on the eastern edge of the high-road, and its curia, with a dedicatory inscription to M. Aurelius by the Senatus Fidenatium, was excavated in 1889. Remains of other buildings may also be seen.

In 27 AD a wooden amphitheatre collapsed i Fidenae resulting in as many as 20,000 dead and wounded out of the total audience of 50,000.