Putin sent troops to Ukraine in February last year, and in September announced a military mobilisation to prop up Moscow's forces in the pro-Western country.
Despite a number of military defeats, victory was "guaranteed, I have no doubt about it," Putin told workers at a factory in Russia's second city Saint Petersburg.
"The unity and solidarity of the Russian people, the courage and heroism of our fighters and, of course, the work of the military-industrial sector" will secure victory, he added.
Putin also praised the Russian defence industry as he spoke at the plant, which is part of Russian missile manufacturer Almaz-Antey. "We have something to rely upon and this cannot but inspire that victory will be ours," he said.
Putin was visiting his native Saint Petersburg to mark the 80th anniversary of Soviet forces breaking the siege of Leningrad as the city was known at the time.
His comments came a week after he replaced Russia's top commander in Ukraine, a move that followed a string of defeats on the battlefield in Ukraine last year.
There is some concern in Russia over how long Moscow's so-called "special military operation" in Ukraine has gone on, with the offensive's anniversary approaching.
Putin once again defended his goals in Ukraine, where he initially sent troops to "de-Nazify" the pro-Western country. "We are absolutely justified in saying that we are fighting neo-Nazism," he said.
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