A turnkey or a turnkey project is a project in which separate entities are responsible for setting up a plant or equipment (e.g. trains/infrastructure) and for putting it into operation. It can include contractual actions at least through the system, subsystem, or equipment installation phase and may include follow-on contractual actions, such as testing, training, logistical, and operational support. It is often given to the best bidder in a procurement process.
Turnkey projects can also be extended, known as turnkey plus, where there is perhaps a small equity interest by the supplier and it will later on continue its operation through a management contract or licensing.
Turnkey refers to something that is ready for immediate use, generally used in the sale or supply of goods or services. The term is common in the construction industry, for instance, in which it refers to the bundling of materials and labor by sub-contractors. A "turnkey" job by a plumber would include the parts (toilets, tub, faucets, pipes, etc.) as well as the plumber's labor, without any contribution by the general contractors.
This is commonly used in motorsports to describe a car being sold with drivetrain (engine, transmission, etc.). A vehicle for sale without these pieces is sold "rolling". A racer may prefer to keep the drivetrain pieces to use in another vehicle to preserve a combination. Similarly, this term may be used to advertise the sale of an established business, including all the equipment necessary to run it, or by a B2B supplier providing complete packages for business start-up.
The term turnkey is also often used in the technology industry, most commonly to describe pre-built computer "packages" in which everything needed to perform a certain type of task (e.g. audio editing) is put together by the supplier and sold as a bundle. This often includes a computer with pre-installed software, various types of hardware, and accessories.