The Rhenish-Westphalian Coal Syndicate (ger.: Rheinisch-Westfälisches Kohlen-Syndikat -RWKS) was a cartel established in 1893 in Essen bringing together the major coal producers in the Ruhr.
The syndicate was set up as coal producers moved towards using shipping rather than railways to deliver their coal to Rotterdam. The cartel co-operated with the Dutch Coal Trade Union, to whom they gave the sole distribution rights for Westphalian coal. Daniël George van Beuningen of the Steenkolen Handels Vereniging was a leading figure in this relationship, greatly increasing the amount of coal imported to Rotterdam and resulting in the cost of using Rhine based barges dropping as their greater use also stimulated technical innovation.
This arrangement led to Rotterdam becoming not just the leading coal transhipment port in the Netherlands but also evolving into the major bunker port in Europe. In 1913 this coal transhipment accounted for over two thirds of the total shipping on the Rhine. By this time the Rhenish-Westphalian Coal Syndicate accounted for 93% of the coal output in the Ruhr and 54% of Germany as a whole.