The visit came after Putin travelled to Crimea on Saturday in an unannounced visit to mark the ninth anniversary of Russia's annexation of the peninsula from Ukraine, and just two days after the International Criminal Court (ICC) issued an arrest warrant for the Russian leader.
Mariupol, which fell to Russia in May after one of the war's longest and bloodiest battles, was Russia's first major victory after it failed to seize Kyiv and focused instead on southeastern Ukraine.
Putin flew by helicopter to Mariupol, Russian news agencies reported citing the Kremlin. It is the closest to the front lines Putin has been since the year-long war. Driving a car, Putin travelled around several districts of the city, making stops and talking to residents.
Mariupol, on the Sea of Azov, was reduced to a smouldering shell after weeks of fighting. The Organization for Security and Cooperation and Europe (OSCE) said Russia's early bombing of a maternity hospital in Mariupol was a war crime.
The ICC issued an arrest warrant on Friday against Putin, accusing him of the war crime of illegally deporting hundreds of children from Ukraine, a highly symbolic move that isolates the Russian leader further.
While Ukraine's President Volodymyr Zelenskiy has made a number of trips to the battlefield to boost the morale of his troops and talk strategy, Putin has largely remained inside the Kremlin while running what Russia calls its "special military operation" in Ukraine.
Kyiv and its allies say the invasion, now in its 13th month, is an imperialistic land grab that has killed thousands and displaced millions of people in Ukraine.
In the Nevsky district of Mariupol, a new residential neighbourhood built by the Russian military, Putin visited an apartment in a newly built residential complex.
"The head of state also examined the coastline of Mariupol in the area of the yacht club, the theatre building, and memorable places of the city," the Interfax agency cited the Kremlin's press service.
Mariupol is in the Donetsk region, one of the four regions Putin moved in September to annex. Kyiv and its Western allies condemned the move as illegal. Donetsk, together with the Luhansk region, comprise most of the Donbas industrialized part of Ukraine that has seen the biggest battle in Europe for generations.
Reuters