The Società della Ferrovia Sicula Occidentale (FSO) was a railway company, no longer in existence, established in 1878 with the aim of building a railway link between Palermo, Marsala and Trapani.

The company was incorporated in Rome as a joint-stock company with a notarial deed dated 3 September 1878 with a paid-up capital of 22 million lire divided into 44,000 shares. It obtained government approval by Royal Decree on 30 September of the same year. It built and inaugurated the first railway link between the two extreme cities of Palermo and Trapani in 1881. Work began with the opening of the first section from the new Palermo Lolli station to Partinico on 1 June 1880. A month later it inaugurated the southern section connecting Trapani to Castelvetrano. In March 1881, it connected Partinico with Castellammare del Golfo, and finally, on 5 June 1881, the entire route was joined with the activation of the central Castellammare del Golfo - Castelvetrano section. In 1882 the Sicula-Occidentale built the junction, from Palermo Lolli to Bivio Madonna dell'Orto, (more recently called Bivio Marittima, for the port of Palermo) to connect to the rest of the network then belonging to the Calabro-Sicula company; the connection was however only used for freight traffic. In 1884 it was listed on the official list of the Milan Stock Exchange[1] To meet its traction needs, the company ordered a group of 14 locomotives from the Reale Opificio di Pietrarsa, delivered between 1880 and 1885, which were framed in the 1-20 group; in 1886 Ansaldo supplied locomotives 35 and 36 of the 35-37 group, and between 1891 and 1895 it delivered a further 6 units of the 1-20 group. Later, again Ansaldo supplied the last unit, 37, in 1901. The company operated the Palermo-Trapani railway via Castelvetrano until 1 August 1907, when it was incorporated into Ferrovie dello Stato. Of the locomotives in group 1-20, 16 units were registered in the new FS group 385, while the three units in group 35-37 were classified as group 388.

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