SSCV Sleipnir is a semi-submersible crane vessel (SSCV) owned and operated by the Netherlands-based Heerema Marine Contractors. It was ordered in 2015 and built in Singapore by Sembcorp Marine. It was named for Sleipnir, the eight-legged horse ridden by Odin in Norse mythology.

The vessel is equipped with two revolving cranes built by Huisman Equipment B.V., each with a capacity of 10,000 t (11,000 short tons); the main cranes can be operated in tandem to jointly lift 20,000 t (22,000 short tons).

After its completion in 2019, SSCV Sleipnir succeeded Heerema's earlier SSCV Thialf as the largest crane vessel in the world.

The vessel is essentially a large platform supported by eight columns (four on each side), with one pontoon per side. Typical SSCVs use larger columns under the cranes to provide support, which can lead to severe pitching in rough seas; SSCV Sleipnir uses columns that are symmetrical fore and aft for calmer motions under higher sea states. The columns are rounded to reduce wave interactions, and the pontoons are streamlined to reduce drag.

The ship's ballast tanks and LNG storage are contained within the eight columns. Each column is 23.75 m (77.9 ft) tall and has a staircase connecting the deck with the pontoon below.

The two large port and starboard tub-mounted cranes are provided by Huisman; overall boom length is 144 m (472 ft). The slewing system, which allows the cranes to rotate in their tub, uses the world's largest bearings at 30 m (98 ft) in diameter. Conventional tub-mounted cranes ride on bogies or wheels, while the Huisman 10,000t cranes use the bearing directly. Prior to the cranes for Sleipnir, the largest bearings Huisman had used for tub-mounted cranes were only 12 m (39 ft) in diameter. The crane house is secured to the foundation using 1,100 bolts 82 mm (3.2 in) in diameter, each weighing more than 40 kg (88 lb), and held in place by nuts.

Each luffing frame weighs 1,170 t (1,290 short tons), and each boom weighs 1,465 t (1,615 short tons). The large port and starboard cranes were fabricated at Huisman's factory in Xiamen, China, and shipped in pieces to Singapore; the BigRoll RoRo ships Baffin (now BigLift Baffin) and Beaufort were used to ferry the crane houses, luffing frames, winch frames and booms along with other large pieces in 2018.

Using the main hoist, each crane is capable of lifting a maximum of 10,000 t (11,000 short tons) at a radius between 27 and 48 m (89 and 157 ft); lifting capacity drops to 7,000 t (7,700 short tons) at a radius of up to 62 metres (203 ft), and 4,000 t (4,400 short tons) at 82 m (269 ft) radius; the maximum operating radius using the main hoist is 102 metres (335 ft). Objects can be lifted and lowered using the main hoist from 20 m (66 ft) below the waterline to 135 m (443 ft) above it when SSCV Sleipnir is operating at its maximum 32 m (105 ft) draft. The main hoists were tested to 110% of rated load using the modified barge H-408 during sea trials in June 2019. These cranes each use approximately 33 km (21 mi) of braided wire rope, 72 mm (2.8 in) thick.