Griner, 31, is a two-time US Olympic champion who plays for the WNBA’s Phoenix Mercury, but was sentenced to nine years in prison for bringing cannabis oil into Russia on Thursday.
Judge Anna Sotnikova sentenced her to nine years in a ‘penal colony’ for carrying two vaping cartridges, which were medically prescribed.
Singer Bieber posted an Instagram story where he offered his help to Griner, saying: “this hurts. If anyone knows any way I can help please let me know.”
Other celebrities also tweeted their shock at the sentence.
Jada Pinkett Smith wrote: “On the same day we got justice for Breonna (Taylor)… I find out that Brittney Griner just got nine years in Russia #FreeBrittney.”
Mia Farrow said the news was “heartbreaking” and added: “The Russian judge ignored everything Britney Griner had stated."
50 Cent said: “This is wild, smh (shaking my head).”
“You don’t ever want to get caught up in the politics, They are gonna tell her like 10 years for a vape pen, watch.”
US President Joe Biden has pledged to continue battling for Griner's release, saying: "Today, American citizen Brittney Griner received a prison sentence that is one more reminder of what the world already knew: Russia is wrongfully detaining Brittney.
"It's unacceptable, and I call on Russia to release her immediately so she can be with her wife, loved ones, friends, and teammates."
Olympian Griner was first detained in February at Moscow Sheremetyevo airport just days before Russia's invasion of Ukraine, but the athlete has just been sentenced.
The White House is reportedly considering a prisoner swap deal which would involve the US handing over arms dealers to Russia in exchange for Griner's release.
Watch: Brittney Griner pleads guilty as Russian court sentences her to nine years