Wärtsilä Oyj Abp, trading internationally as Wärtsilä Corporation, is a Finnish company which manufactures and services power sources and other equipment in the marine and energy markets. The core products of Wärtsilä include technologies for the energy sector, including gas, multi-fuel, liquid fuel and biofuel power plants and energy storage systems; and technologies for the marine sector, including cruise ships, ferries, fishing vessels, merchant ships, navy ships, special vessels, tugs, yachts and offshore vessels. Ship design capabilities include ferries, tugs, and vessels for the fishing, merchant, offshore and special segments. Services offerings include online services, underwater services, turbocharger services, and also services for the marine, energy, and oil and gas markets. At the end of December 2022, the company employed 17,500 workers.

Nils Ludvig Arppe was a Finnish industrialist.