The Walrus-class submarine is the only submarine class currently in operation in the Royal Netherlands Navy. They have been in service since 1990 and are all named after sea mammals.

In 1974 the Royal Netherlands Navy made it known, through the defensenote 1974, that it wanted to replace the Dolfijn-class submarines. Since the 1960s the Royal Netherlands Navy was doing studies and research into what kind of submarines they wanted to build.The results were that the Netherlands should build conventional diesel-electric submarines, since nuclear submarines are costly and can only be paid by countries with major navies such as the United States, France and the United Kingdom. Nonetheless, even with the diesel-electric submarine the Dutch government also wanted to look if they could try to work togheter with international allies for the construction because else it would lead to more costs.

Between 1975 and 1978 the design of the Walrus-class was for the most part completed, and included many improvements which would result in the new submarines being state of the art and a significant improvement over previous submarines in use by the Royal Netherlands Navy. For example, a special kind of French steel was used to construct the hull of the Walrus-class submarines which would be more elastic, and allowed the submarines of this class to dive deeper than previous submarines. Furthermore, there was a focus on automation,aimed at decreasing the manpower needed to operate the submarine and at the same time making them more effective against threats. On 19 June 1979 the Dutch Minister of Defense, Willem Scholten, signed a contract worth 425 million guilders with the Rotterdamsche Droogdok Maatschappij to build 2 submarines to replace the Dolfijn-class submarines, with the construction of the second boat to be started in the following year. Already soon RDM noticed that the new submarines could not be built the same way as the Zwaardvis-class submarines, since it had to use new technique to build the submarines. Another problem was that because the design was not completed and constantly modified to incoorporate new developments in the submarine world, which led to issues during the building process, the construction proceeded slowly. Nonetheless, the construction continued and on 11 October 1979 the HNLMS Walrus was laid down. 2 years later, on 24 September 1981, the HNLMS Zeeleeuw was also laid down.

On 19 February 1983 the parent company of RDM, the shipbuilding company Rijn-Schelde-Verolme, went to everyone's surprise bankrupt even after the Dutch government provided 2,2 billion guilders state aid. This was problematic because the construction of the Walrus-class submarines were far from being completed. To make sure the construction of the submarines was continued RDM was re-established as an independent company. Furthermore, the Royal Netherlands Navy ordered also an additional 2 submarines of the Walrus-class earlier than planned to help RDM financially. However, at this time the Walrus-class submarines was still plagued with many problems.

New problems arose on 14 August 1986, when the command center of the HNLMS Walrus caught fire, while it was still on a scaffold in the yard. The fire lasted about five hours and resulted in immense damage to the submarine, the commando central was completely burned out, including all the recently installed equipment. Some equipment could be rescued, but most had to be replaced.This delayed the construction of the submarines once again. The costs of the resulting damage were 225 million guilders, however, the damage was luckily fully covered by insurance.The exact location, origin and cause of the fire was never found out. Presumably, the fire was caused in the vicinity of the corporals and men washroom by a defect in the electrical work lighting. The damaged submarine was repaired and in 1987 it was reported that these repairs had been completed. Due to the fire, the construction of the Walrus was so delayed that the second submarine with construction number 349 was put into service as the first submarine of the Walrus-class with the name HNLMS Zeeleeuw. The HNLMS Walrus was put into service two years later. The two other boats were put into service as HNLMS Dolfijn and HNLMS Bruinvis. The delays also meant that the HNLMS Dolfijn, the HNLMS Potvis and the HNLMS Tonijn of the Dolfijn-class had to remain in service longer than planned. All the problems, delays and rising costs were eventually dubbed by the Dutch national parliament as the Walrus-affair. Nonetheless, at the time of their commissioning, the Walrus-class submarines were considered to be one of the most modern and advanced conventional submarines that were operational at the time.

Class overview
Name:	Walrus class
Builders:	Rotterdamsche Droogdok Maatschappij
Operators:	Royal Netherlands Navy
Preceded by:	Zwaardvis class
Cost:	ƒ500m per unit (1992 prices)
Built:	1979–1992
In commission:	1990–present
Completed:	4
Active:	4
General characteristics
Type:	Diesel-electric attack submarine
Displacement:	2,350 t surfaced, 2,650 t submerged, 1,900 t standard
Length:	67.73 m (222.2 ft)
Beam:	8.4 m (28 ft)
Draft:	6.6 m (22 ft)
Propulsion:	3 diesels, diesel-electric, 5,430 shp (4 MW), 1 shaft, 5 blades
Speed:	13 knots (24 km/h) surfaced, 20 knots (37 km/h) submerged
Range:	18,500 km (10,000 nmi) at 9 kn (17 km/h)
Test depth:	>300 m (980 ft)
Complement:	50 to 55
Sensors and processing systems:	Surface Search Radar: Signaal/Racal ZW 07 Sonar Systems: Thomson Sintra TSM 2272 Eledone Octopus GEC Avionics Type 2026 towed array Thomson Sintra DUUX 5 passive ranging and intercept
Armament:	4 × 21-inch (533 mm) torpedo tubes (20 × Honeywell Mk 48 or HoneywellNT 37 torpedoes mines, SubHarpoon SSM)