Nasrin Sotoudeh was jailed last month for "acting against national security" and for being a member of the Defenders of Human Rights Center founded by Nobel Peace Prize laureate Shirin Ebadi.
The case is considered part of a broader crackdown on human rights lawyers and activists in Iran.
Sotoudeh was a prominent defender of civil activists, especially women, and represented a number of opposition figures and activists arrested in the unrest after the disputed 2009 presidential election.
In a statement posted February 9 on the award-winning Iranian women's rights website we-change.org, the signatories condemn the charges against Sotoudeh, saying she had been put on trial for defending human rights, women's rights, and political prisoners.
The signatories include lawyers, writers, academics, journalists, and rights activists. Most are based outside Iran though the list includes a few inside the Islamic republic.
The signatories include Norway-based activist Asieh Amini; Parastou Forouhar, the Germany-based daughter of two murdered Iranian dissidents; Parvin Ardalan, a member of the One Million Signature Campaign against discriminatory Iranian laws; Roya Toloui, a Kurdish activist who fled Iran and sought asylum in the United States; and Shadi Sadr, a well-known women's rights advocate who was forced to leave Iran.
The statement also expresses concern that Sotoudeh's family is coming under pressure for pursuing her case.
Reza Khandan, Sotoudeh's husband, was briefly detained last month over his inquiries regarding his wife and his efforts to publicize the case.
Nasrin Basiri, a journalist and activist based in Berlin, told Radio Farda such moves are aimed at suppressing the voices of people and keeping a closed atmosphere within the country where no one can question the authorities.