The 35-year-old army helicopter pilot flew home as part of an apparent prisoner swap with Moscow, with two alleged Russian soldiers leaving Ukraine earlier in the day.
"I'm ready to once again give my life for Ukraine on the battlefield," a defiant Savchenko declared as she touched down on home soil, wearing a white T-shirt bearing the Ukrainian trident, a national symbol.
A presidential motorcade was on standby at Kiev's main Boryspil airport to whisk Savchenko to Poroshenko's office where she was to be decorated by the president, two sources told AFP.
While in prison, she launched several hunger strikes to protest her detention, refusing both food and water during her high-profile trial in southern Russia.
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She constantly defied the Russian authorities and even raised her middle finger at the court in March.
Kiev and its Western allies view Savchenko as the latest pawn in Moscow's broader aggression against Ukraine that has seen Russia seize the Crimean peninsula and fuel the separatist uprising in 2014.
Savchenko, an Iraq war veteran, was convicted in March over the killing of two Russian journalists in eastern Ukraine and sentenced to 22 years behind bars. She had been held in captivity in Russia since June 2014.
The crop-haired military helicopter pilot denies any involvement in the shelling deaths of two Russian state television reporters.
Kiev has long been pushing for a prisoner swap to free Savchenko, and Poroshenko said in late April that he hoped she would return home "in a few weeks."
"But we have been able to prove that there are no insurmountable tasks and we've managed to free the hostage from the jaws of Mordor," he added, referring to a savage land in the "Lord of the Rings" trilogy.
Earlier in the day, two alleged Russian soldiers, Aleksandr Aleksandrov and Yevgeny Yerofeyev, sentenced by Ukraine to 14 years in prison for fighting in the rebel-held east, arrived in Moscow, Russian national television reported.