The Altona-Kiel Railway Company was a joint-stock company, established under the law of Denmark in personal union with the Duchy of Holstein, that built and operated an 105 km railway line between Altona and the Baltic Sea port city of Kiel. Altona was at that time the second largest city under Danish rule and the railway line was the first built in Danish-controlled territory.

The Hamburg-Altona–Kiel railway is one of the most important main line railways of the states of Schleswig-Holstein and Hamburg in Northern Germany. The line runs through the region of Holstein and connects the cities of Hamburg, Elmshorn, Neumünster and Kiel. The 105 km (65 mi) long standard gauge double track electrified railway line is now owned by DB Netz.