This article lists anniversary events related to rail transport that occurred on October 3.

• 1839 – The first railway line in Italy, 7 km between Naples and Portici, opens.
• 1873 – Grand Trunk Railway begins converting its track between Stratford, Ontario, and Montreal from 5 ft 6 in (1,676 mm) (broad gauge) to 1,435 mm (4 ft 8+1⁄2 in) (standard gauge); the conversion is completed within 24 hours.

• 2001 – Canadian Pacific Corporation divests itself of its five major subsidiaries, spinning off Canadian Pacific Railway as an independent company.
• 2004 – The Southwestern Railroad leases the Carlsbad Subdivision (183 miles of track between Clovis and Carlsbad, New Mexico) from the Burlington Northern and Santa Fe Railway.
• 2005 – The overcrowded Bundelkhand Express from Varanasi to Gwalior, India, speeds too fast through a sharp turn in the track and derails, killing 16 people. See: Datia train crash.

• 1928 – Edward L. Moyers, president of MidSouth Rail and Illinois Central Railroad, chairman and CEO of Southern Pacific Railroad, "Railroader of the Year" for 1995, is born (d. 2006).^[1]

• 1907 – Jacob Nash Victor, oversaw construction for the California Southern Railroad from San Diego through Cajon Pass to Barstow, California (b. 1835).