The $1.3 billion commuter train will connect Dakar with Diamniadio, an industrial city being built entirely from scratch on a dusty plain about 40 kilometres (25 miles) away.
The first new railway since independence from France in 1960 is a cornerstone of President Macky Sall's Senegal Emergent plan, which includes a new airport, roads, sports arenas and a sleek conference centre.
About 115,000 passengers are expected to commute daily on the train between Dakar and Diamniadio, the government said. Further extensions will connect the main airport and eventually other cities and towns in the coming years.