The procedure was greeted by wild applause by the crowds crammed into the city's state theatre to witness the procedure as the burly French megastar grinned broadly.
"Glory to Saransk, Glory to Mordovia, Glory to Russia!" he bellowed in celebration, in heavily-accented Russian.
Depardieu then proudly produced the Russian passport, complete with the new registration stamp, to show off to the cameras, an AFP correspondent said.
His address was announced as an apartment on No. 1, Democracy Street in an upscale area of Saransk which belongs to relatives of his friend, the head of Russia's State Film Fund Nikolai Borodachev.
All Russian citizens are obliged to be formally registered as living in a certain city, town or village with a corresponding stamp in their passport to prove it.
Depardieu was granted a Russian passport by President Vladimir Putin in January after complaining at high tax rates in France. This trip is his second to Russia as a Russian citizen and he is expected to stay in Saransk for several days.
True to his reputation for rocking relations with his home country, Depardieu aggressively asked a pair of French journalists whom he recognised to leave and delete their video recordings.
The Mordovia region in central Russia was until know chiefly known for its network of prison camps where one of the jailed Pussy Riot punks is serving her sentence.
Populated by a large community of Finnic-speaking Mordvins, it is also a host city of the 2018 World Cup that is to be hosted by Russia.
"We are very happy that the citizen of the world, the great actor Gerard Depardieu, has registered namely in Saransk," said the head of the Mordovia region, Vladimir Volkov.
"We will continue to get Depardieu acquainted with our culture, our agriculture, industry, our successful experience of inter-ethnic relations and our people," he added.
Local media reports said that Depardieu on his latest trip would be given an excursion around a local cheese factory that uses French machinery and may also go on a trip hunting for wild boar.
According to Yuri Mishanin, the head of the theatre where the registration ceremony was held, Depardieu was also hoping to "open a small restaurant here in Saransk".
The Russian authorities are clearly delighted to have found a cultural figure who praises Putin to the skies and shows his respect for Russian culture.
But some commentators have queried Depardieu's wanderings in Putin's Russia, comparing him to artists like Irish writer George Bernard Shaw who praised the Soviet Union at the height of Stalin's tyrannical rule.
Depardieu was given citizenship by Putin in early January after he squabbled with French Prime Minister Jean-Marc Ayrault, who scolded his "pathetic" decision to become a tax exile in Belgium.
He is not expected to live full time in Russia but the Saransk authorities are expecting he will make regular visits to his adopted new home.
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