"I just want to say a few words about Pussy Riot," the queen of pop told a raucous crowd at Olimpiysky Stadium in Moscow.
"I'm blessed to be from a country where I have the right to express my opinion, okay. But my dream and my prayer is that everyone in the world has this right. Not only here in Russia, but in France, in Iran, everywhere in the world."
"I think they have done something courageous," Madonna said of Pussy Riot. "I pray for their freedom."
Nadezhda Tolokonnikova, 23, Maria Alyokhina, 24, and Ekaterina Samutsevich, 29, put on a brief show at Moscow's preeminent Orthodox church, Cathedral of Christ the Savior in March, singing lyrics like "Mother of God, drive Putin away."
Accused of "abusing God" and "hooliganism motivated by religious hatred," by Russian prosecutors, the three women face up to seven years in prison for showing "real mockery and humiliation directed at the people in the church," according to the UK's Telegraph.
The women have all apologized in court and Tolokonnikova called their cathedral gig an "ethical mistake."
Other musicians have joined the international chorus of Pussy Riot supporters who believe the trial demonstrates Russia's worsening attitude toward Western influence and political opposition, masked by insincere concern for the Orthodox Church.
According to Billboard, Red Hot Chili Peppers, Franz Ferdinand, Peter Gabriel and Sting have all condemned Russia's actions.
"Nadya and Katya and Masha, we love you," Anthony Kiedis of the Red Hot Chili Peppers told a crowd in Moscow.
"We love to support you and are here to help you," he added.
Franz Ferdinand's Alex Kapranos took to Twitter to express thinly veiled criticism of Russian President Vladmir Putin.
Even "It's Always Sunny in Philadelphia's" Danny DeVito has weighed in, tweeting "Mr. Putin...Pussy Riot...set 'em free."