The US company has been working with Atlantis on the turbine’s design since 2013.
It will be one of four turbines in the phase one of the MeyGen project and is due to arrive in Scotland for installation in 2016.
Lockheed Martin will manufacture the turbine’s steel housing and assemble all the modules, including the gearbox and generator.
Atlantis CEO Tim Cornelius said: "This new multi-million pound contract with Lockheed Martin further develops the strong relationship that exists between the two companies who are at the forefront of tidal power generation."
Construction on phase one of the project is expected to start later in 2014 with the first power planned to be delivered to the grid by 2016.
The first phase of the project is expected to generate about 86MW of electricity, enough to meet the energy needs of approximately 42,000 homes.
Swiss power technology firm ABB will provide the onshore grid connection for the first phase of the project.
SmartestEnergy has agreed to buy the electricity generated from the project under a 10-year power purchase agreement.
A technical resource of 29 terawatt hours of energy per year (TWh) is estimated to be available in the UK’s tidal currents, of which 11TWh is identified in the tidal flows in the Pentland Firth in the far north of Scotland.
