The first of four 1.5MW turbines was recently installed in the Pentland Firth as part of the initial phase of the 400MW MeyGen tidal array project.
It has now been powered up and begun supplying renewable electricity to the national grid.
When fully completed the scheme will have up to 269 turbines, with the potential to supply 175,000 homes.
The inaugural turbine was successfully put in place last week and plugged into a pre-laid cable that connects to the onshore control centre and grid export point.
The device is the first to become operational in the primary 6MW phase of the development, which will have a total build out of 398MW.
Over the past few days engineers have been working to establish communications with the turbine and verify that on-board safety and monitoring systems are functioning.
Electricity is produced using only the tidally driven water flows that rush through the Inner Sound of the Pentland Firth.
The scheme is being developed by marine energy firm Atlantis Resources, with backing from Scottish Enterprise, Highlands and Islands Enterprise, the Crown Estate and the UK government’s former Department for Energy and Climate Change.
“This is the moment we have been working towards since we first identified the MeyGen site back in 2007, and I am immensely proud of and grateful for the remarkable team of people who have contributed to this milestone,” said Atlantis chief executive Tim Cornelius.
“I look forward to bringing more news of the project development over the coming weeks and months as we move into the full operational phase.
“It’s especially exciting to be making this announcement on the morning after the first ‘supermoon’ in 68 years – last night those of us with clear skies were able to get a good view of the powerhouse behind tidal energy, and be reminded that even in times like these there are still predictions we can rely on.
“The success of this first phase is a foundation for the tidal industry to build upon to ensure we develop a new energy sector which can deliver clean, predictable and affordable power from the UK’s own abundant resources.
“When it comes to energy, we think consumers should be asking for the moon, and we know how to harness it.”
Two turbines installed off the coast of Shetland earlier this year became the first offshore tidal array in the world to deliver electricity to the grid.
Environmentalists have welcomed the latest turbine going online, saying it would contribute to efforts to combat climate change.
“News of the first electricity to come from what will hopefully become one of the world’s largest tidal power schemes is a really exciting moment,” said Lang Banks, director of campaign group WWF Scotland.
“Coming only a few months after turbines off Shetland generated their first power, it’s a sign that Scotland is really starting to make progress in harnessing the power of our seas.
“Along with action to improve energy-efficiency, marine renewables have the potential to play a role in powering our homes and businesses in the future.”