Alexander L. Kielland was a Norwegian semi-submersible drilling rig that capsized while working in the Ekofisk oil field in March 1980, killing 123 people. It was a platform of the Pentagone series.

The capsize was the worst disaster in Norwegian waters since World War II. The rig, located approximately 320 km east of Dundee, Scotland, was owned by the Stavanger Drilling Company of Norway and was on hire to the U.S. company Phillips Petroleum at the time of the disaster. The rig was named after the Norwegian writer Alexander Lange Kielland.

The rig was built as a mobile drilling unit at a French shipyard, and delivered to Stavanger Drilling in July 1976. The floating drill rig was not used for drilling purposes but served as a semi-submersible 'flotel' providing living quarters for offshore workers. By 1978 additional accommodation blocks had been added to the platform, so that up to 386 persons could be accommodated.In 1980, the platform was working in the Norwegian North Sea providing offshore accommodation for the production platform Edda 2/7C.Within a few days it was scheduled to start a new contract with Shell UK as a drilling rig.