Pioneering Spirit (formerly Pieter Schelte) is a catamaran crane vessel owned by the Switzerland-based Allseas Group designed for the single-lift installation and removal of large oil and gas platforms, and pipelines.

[7] The initial idea featured two rigidly connected, self-propelled supertankers, with a large slot at the bows enabling it to install platform topsides in one piece.

[9] The decision was prompted by a lack of suitable vessels to convert, the lower costs associated with a new-build, and the need to house sophisticated equipment – such as a dynamic positioning system – in the hull.

[4] In 2007, twenty years after the idea was first conceived, Allseas announced plans to build the Pieter Schelte, a twin-hulled platform installation / decommissioning and pipelay vessel.

The design also included pipelay equipment to handle pipe diameters ranging from 15–175 cm (6–68 inches) at water depths exceeding 4,000 m (13,000 ft).

[12][13] After the global financial crisis weakened funding, the company was forced to postpone the building schedule and as a result delayed the awarding of the hull construction contract.

[24] In September 2021, a set of sheerlegs with a lifting capacity of 20,000 tonnes was installed on the stern deck of the ship, permitting it to also hoist platform jackets.

[6] Pioneering Spirit is the world's largest vessel, in terms of her gross tonnage (403,342 gt), breadth (123.75 m or 406 ft), and displacement (1,000,000 tonnes or 980,000 long tons).

Two tilting lift beams for the installation or removal of the steel jackets used for fixed platforms, up to 25,000 tonnes (28,000 short tons) in weight, will be located at the vessel's stern.

[26] Pioneering Spirit performed her first commercial lift, removal of Repsol's 13,500-tonne (14,900-short-ton) Yme mobile offshore production unit (MOPU) on 22 August 2016.

[33] Located in the Yme field in the Norwegian sector of the North Sea, approximately 100 km (54 nautical miles) west of Stavanger, the MOPU was a jack-up type platform standing on three, 3.5-metre (11 ft) diameter steel legs.

[2][34] Located in the Brent field, approximately 186 km (100 nautical miles) off the northeast coast of Shetland, the iconic platform sat on a three-legged gravity-based structure in 140 m (460 ft) of water.

[35] Pioneering Spirit installed the offshore section of SouthStream Transport B.V's dual 930-kilometre (580 mi) Turkish Stream pipeline in the Black Sea.

[38] Starting from the Russian coast near the town of Anapa, the 930-kilometre (580 mi), 80-centimetre (32 in) diameter twin-pipeline will traverse the Black Sea at depths up to 2,200 m (7,200 ft) and emerge onshore in Turkey's Thrace region.