San Giovanni, Roman Catholic church in Nettuno, Italy

San Giovanni is the parish church of Nettuno, with a facade facing east divided by a string course into two registers with paired pilasters. The lower register has a round-arched portal; the upper, narrower and flanked by volutes, has a rectangular window and a triangular pediment set within a semicircular one. Inside is a single nave with pilasters and a barrel vault with lunettes.

The church stands on the site of a pagan temple dedicated to Neptune; the medieval collegiate church that replaced it held the title 'mother church of Anzio and Conca', as recorded in Cardinal Emilio Altieri's 1636 visitation report. The old building was demolished in 1738, and the new parish church, designed by Carlo Marchionni, was completed in 1748.

For centuries the parish held the title of mother church of Anzio and Conca, a privilege inherited from the suppressed diocese of Anzio; Cardinal Emilio Altieri's 1636 visitation report records it. The church stands on the site of a pagan temple to Neptune and was dedicated to the Assumption of the Virgin Mary before receiving its present dedication to Saints John the Baptist and Evangelist.

The church faces east, so the facade is best seen in morning light. It stands in the historic centre of Nettuno, within easy walking distance of the harbour and the town's other main streets. The interior is a single nave, entered through the main portal on the facade.

The church stands on the site of a pagan temple dedicated to the god Neptune, from whom Nettuno takes its name. For centuries the parish held the title "mother church of Anzio and Conca", a privilege inherited from the suppressed diocese of Anzio, as recorded in Cardinal Emilio Altieri's 1636 visitation report.