US basketball player Brittney Griner has been released by Russia in a prisoner swap.
US officials said she is US custody.
The two-time Olympic gold medallist was arrested on 17 February at a Moscow airport with vape cartridges containing cannabis oil, which is banned in Russia.
She was sentenced on 4 August to nine years in a penal colony.
Ms Griner apologised for what she said was an honest mistake, telling an appeal hearing in October that she used medical cannabis to relieve the pain from a series of sports injuries. Both recreational and medicinal uses are prohibited in Russia.
US officials said President Joe Biden, Vice-President Kamala Harris and Secretary of State Antony Blinken had all spoken to Ms Griner by phone, reporting that she is good spirits.
Moments ago I spoke to Brittney Griner.— President Biden (@POTUS) December 8, 2022
She is safe.
She is on a plane.
She is on her way home. pic.twitter.com/FmHgfzrcDT
Russia's foreign ministry said it had traded Ms Griner for Russian citizen Viktor Bout.
The exchange took place at Abu Dhabi airport, Russian news agencies reported.
Bout was one of the world's most wanted men during his career as an international weapons dealer, and was dubbed "the Merchant of Death" in a 2007 biography.
Born in Dushanbe, Soviet Tajikistan, in 1967, Bout is reported to be fluent in several languages and to have served in the Soviet army as a military translator, including in Angola.
He has said he attended a Moscow language institute that serves as a training ground for military intelligence officers.
Bout was arrested in 2008 in Thailand after a sting operation by US agents who recorded him offering to sell missiles to people he believed were leftist Colombian guerrillas.
In 2012, he was given a 25-year prison sentence by a US court on multiple charges related to his arms dealing career.
Russia has always proclaimed his innocence, describing his case as a glaring injustice and attempting to secure his release.