HNLMS Mercuur (A900) is a submarine support ship of the Royal Netherlands Navy.

The ship can also do launch tests for the Mark 48 torpedo, which are used by all Dutch submarines since the Zwaardvis class entered service in the 1970s.

On 21 August 1987 Mercuur was put into service and has been serving ever since, with a minor break for implementing upgrades during her modernization.

In 2015 Damen Group won an order for the maintenance and modernization of the torpedo support ship Mercuur.

[5] The ship underwent modifications including; a different design of the bridge, a whole range of new electronic equipment, and a reinforced bow.

Mercuur arrived on 7 September 2015 at Damen Shipyards Den Helder for her modernization to start.