The Junkers L 5 was a six-cylinder, water-cooled, inline engine for aircraft built in Germany during the 1920s.

It was a water-cooled upright inline 6-cylinder unit, four-stroke and petrol-fuelled, with a capacity of nearly 23 litres.

The splash component of the L2's lubrication was abandoned in favour of a completely forced recirculating system.

[3] The best demonstration of the reliability of the L5 was given by the unit which powered the single-engined W 33 Bremen in the first fixed wing east to west crossing of the Atlantic in April 1928.

For this flight the compression ratio was raised to 7:1 to provide sufficient power for the heavily fuelled aircraft at take off.