As a supplement to the series 340 based on the German V 200, RENFE had the series 333 built from 1974. These heavy six-axle diesel locomotives were based on the Danish MZ, which was in turn based on the EMD model JT26. They are intended for passenger and freight service and have the two-stroke V16 engine of the 645 series with 2,460 kW. They were the first Spanish diesel locomotives to have electric train heating.

Between 2000 and 2005, 92 of 93 locomotives were fundamentally rebuilt by Alstom and designated 333.3. Since only the engines, generators and train protection systems were retained, it was actually a completely new building. The traction electrics and electronics are now much more modern and the car body is similar to that of the Alstom Prima. While these are intended for freight trains with a maximum speed of 120 km/h, eight were again converted to 160 km/h and designated 333.4.