The railway from Amsterdam through Haarlem to Rotterdam (also: Oude Lijn, Dutch for "old line") runs from Amsterdam Centraal to Rotterdam Centraal through Haarlem (and The Hague).

From December 2011 it is used by all direct trains from Amsterdam to The Hague, and all direct supplement-free trains from Amsterdam to Rotterdam except those through Woerden.

It contains the oldest railway line in the Netherlands, and follows the old horse-drawn boat (Dutch: trekschuit) canal route from Leiden via Haarlem to Amsterdam-Sloterdijk.

The oldest section, opened in 1839, ran from Amsterdam to Haarlem.

On 2 August 2024 the doubling of the tracks was completed after a long delay.