Thousands of people were at the ceremony at BAE Systems' Devonshire Dock Hall in Barrow to mark the end of the build process for Artful.
Another four of the nuclear-powered submarines are being built at the yard.
The ceremony was carried out by Amanda Lady Zambellas, wife of the Royal Navy's First Sea Lord, Admiral Sir George Zambellas.
BAE Systems Maritime - Submarines managing director John Hudson said: "The design and build of a nuclear-powered submarine is as challenging as it is complex, so today represents a significant milestone in Artful's programme.
"It requires real skill and innovation to deliver submarines as sophisticated as Artful and this would not have been possible without the valued contribution of our employees and the collaborative efforts of the whole submarine enterprise."
Artful will remain at the Barrow yard while commissioning activities are carried out and is due to be launched early next year for further tests.
HMS Astute and HMS Ambush have already been launched. The other vessels are at various stages in the design and build process and will be called Audacious, Anson, Agamemnon and Ajax.
The Barrow yard has been working on the Astute programme since 2001.
The Ministry of Defence said the Astute class of submarines have greater firepower, state-of-the-art communications equipment and advanced stealth technology, making them quiet and harder to detect.
The third Astute Class submarine to be built at a Cumbrian shipyard has been named.