Control over Mariupol has given Moscow a crucial foothold on the Sea of Azov.
Putin can now achieve a key objective - a land bridge between Russia and the Crimean peninsula.
Mariupol acted as a gateway for Ukrainian exports, control over the city is helping Putin meet the aim of strangulating Ukraine's economy.
Russia briefly controlled Mariupol earlier too, after the ouster of the pro-Kremlin Ukrainian President in 2014.